JP4609404B2 - Liquid crystal display capable of limiting viewing angle - Google Patents

Description

  The present invention relates to a liquid crystal display device capable of limiting a viewing angle.

  The liquid crystal display element has a wide viewing angle. Therefore, there is a possibility that the display is peeped by others from an oblique direction (a direction inclined with respect to the normal direction of the liquid crystal display element).

As a liquid crystal display device for preventing peeping, a viewing angle limiting element for reducing visibility from a direction inclined with respect to the front direction is disposed on one surface side of the liquid crystal display element, and a wide viewing field is provided. There has been proposed a liquid crystal display device capable of performing a corner display and a high security narrow viewing angle display without a possibility of being peeped by a third party. (See Patent Document 1)
This viewing angle limiting element is provided with a plurality of segmented regions on each of the inner surfaces facing each other of a pair of substrates, and an electrode having a predetermined shape is formed corresponding to each segmented region. The liquid crystal molecules encapsulated between a pair of substrates are tilted in an orientation state having a viewing angle in a direction tilted in one direction with respect to the normal direction of the liquid crystal display element, and in a direction opposite to that direction. In an orientation state having a viewing angle in the selected direction.

  The liquid crystal display device limits the viewing angle of the display image of the liquid crystal display element by reducing the visibility from an oblique direction by applying a voltage between the electrodes of the viewing angle limiting element.

That is, when a voltage is not applied between the electrodes of the viewing angle limiting element, that is, when the viewing angle limiting element is in a non-display state, the display image of the liquid crystal display element can be seen with a wide viewing angle. On the other hand, when a voltage is applied between the electrodes of the viewing angle limiting element, the liquid crystal display element of the liquid crystal display element is viewed from a direction inclined in one direction with respect to the front direction and a direction inclined in the opposite direction. The electrode having the predetermined shape for each segmented region having a viewing angle in a direction tilted in one direction of the viewing angle limiting element and each segmented region having a viewing angle in a direction tilted in the opposite direction. A display corresponding to is displayed and is hidden by this display. Therefore, the display image of the liquid crystal display element cannot be recognized from the one direction and the direction inclined in the opposite direction, the viewing angle of the display image is apparently limited, and the viewing angle of the display image is narrow. Become.
JP 2004-133334 A

  However, the viewing angle limiting element in which the liquid crystal molecules are aligned in different alignment states for each of the divided regions obtained by dividing the region corresponding to the screen of the liquid crystal display element into each of the divided regions on the inner surfaces of the pair of substrates. Manufacture is difficult because a complicated alignment process (rubbing process of the alignment film) having a different direction must be performed.

  An object of the present invention is to provide a liquid crystal display device capable of limiting the viewing angle. Another object of the present invention is to provide a liquid crystal display device capable of controlling the viewing angle between wide viewing angle display and narrow viewing angle display.

In order to achieve the above-described object, a liquid crystal display device according to the first aspect of the present invention provides
A liquid crystal display element having a liquid crystal layer and a first polarizing plate ;
A surface light source for irradiating the liquid crystal layer with light through the first polarizing plate ;
A viewing angle limiting element disposed between the first polarizing plate and the surface light source ;
With
The viewing angle limiting element is:
A first substrate and a second substrate which are arranged so as to face each other and the facing distance is variable,
The first substrate is disposed on the surface facing the second substrate so as to protrude from the facing surface toward the second substrate, and gives a phase difference of ½ wavelength to the transmitted light. 1 retardation layer;
The second substrate is disposed on the surface facing the first substrate so as to protrude from the facing surface toward the first substrate, and gives a phase difference of ½ wavelength to the transmitted light. Two retardation layers;
A second polarizing plate disposed so that a transmission axis is orthogonal to the transmission axis of the first polarizing plate;
With
The second substrate is disposed between the first substrate and the second polarizing plate,
The second polarizing plate is disposed between the second substrate and the surface light source,
The first retardation layer and the second retardation layer are alternately arranged when viewed from above in a predetermined direction .

A liquid crystal display device according to the second aspect of the present invention provides:
A liquid crystal display element having a liquid crystal layer and a first polarizing plate;
A surface light source for irradiating the liquid crystal layer with light through the first polarizing plate;
A viewing angle limiting element disposed between the first polarizing plate and the surface light source;
With
The viewing angle limiting element is:
A first substrate and a second substrate which are arranged so as to face each other and the facing distance is variable,
A first retardation layer disposed on a surface of the first substrate facing the second substrate so as to protrude from the facing surface toward the second substrate;
A second retardation layer disposed on a surface of the second substrate facing the first substrate so as to protrude from the facing surface toward the first substrate;
A second polarizing plate disposed so that a transmission axis is orthogonal to the transmission axis of the first polarizing plate;
With
The second substrate is disposed between the first substrate and the second polarizing plate,
The second polarizing plate is disposed between the second substrate and the surface light source,
The first retardation layer is configured such that a slow axis of the first retardation layer is parallel to a slow axis of the second retardation layer and transmitted through the second polarizing plate. Arranged at an angle of 45 ° to the axis,
The first retardation layer and the second retardation layer are alternately arranged when viewed from above in a predetermined direction.

According to the present invention, the viewing angle can be controlled in the wide viewing angle display and the narrow viewing angle display.

Embodiment 1 FIG.
1 to 10 show a first embodiment of the present invention. FIG. 1 is an exploded perspective view of a liquid crystal display device, and FIG. 2 is a side view of the liquid crystal display device.

  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 an observation side of the liquid crystal display element 1 (FIGS. 1 and 2, the surface light source 7 that is disposed on the opposite side to the liquid crystal display element 1, and the viewing angle limiting element disposed between the liquid crystal display element 1 and the surface light source 7. 10.

  The liquid crystal display element 1 is an active matrix liquid crystal display element, the internal structure of which is not shown, but of the inner surfaces facing each other of a pair of transparent substrates 2 and 3 joined via a frame-shaped sealing material 4, A plurality of transparent pixel electrodes arranged in a matrix in the row direction (horizontal direction of the screen) and the column direction (vertical direction of the screen) on the inner surface of one substrate, for example, the substrate 3 opposite to the observation side, and A plurality of TFTs (thin film transistors) respectively connected to the pixel electrodes, a plurality of gate wirings connected to the TFTs in each row, and data wirings connected to the TFTs in each column are provided. On the other substrate, that is, on the inner surface of the observation-side substrate 2, a single transparent transparent electrode facing the plurality of pixel electrodes, and a plurality of regions comprising the plurality of pixel electrodes and the counter electrode facing each other Three color filters of red, green, and blue are formed corresponding to the pixels. A liquid crystal layer is sealed in a region surrounded by the sealing material 4 between the pair of substrates 2 and 3.

  The liquid crystal display element 1 is a TN (twisted nematic) type liquid crystal display element in which the liquid crystal molecules of the liquid crystal layer are twist-oriented between the pair of substrates 2 and 3 at a substantially 90 ° twist angle. And a pair of polarizing plates 5 and 6 disposed on the opposite side.

  Note that the liquid crystal display element 1 of this embodiment is of a normally white mode. Of the pair of polarizing plates 5 and 6, the polarizing plate 5 on the observation side has a transmission axis 5a substantially 45 in one direction with respect to the horizontal axis 100 of the screen, for example, counterclockwise when viewed from the observation side. The polarizing plate 6 on the opposite side is arranged in a direction inclined at an angle, and its transmission axis 6 a is arranged so as to be substantially orthogonal to the transmission axis 5 a of the observation side polarizing plate 5.

  The surface light source 7 includes a light guide plate 8 made of a plate-shaped transparent member, and a plurality of light emitting elements 9 such as LEDs (light emitting diodes). The light guide plate 8 is formed with an incident end face 8a for making light incident on one end face thereof, and an exit face 8b for emitting light incident from the incident end face 8a is formed on one of the two plate faces, and the other plate face. A reflection surface 8c is formed that reflects light incident from the incident end surface 8a toward the emission surface 8b. The light emitting element 9 is disposed to face the incident end face 8a of the light guide plate 8.

  The surface light source 7 causes light from the light emitting element 9 to enter the light guide plate 8 from its incident end face 8a, and emits the light from the entire area of the light exit surface 8b of the light guide plate 8 in the normal direction of the light guide plate 8. In contrast, the light is emitted in a spread angle range having a substantially uniform angle in the entire circumferential direction.

  On the other hand, the viewing angle limiting element 10 directs illumination light from the surface light source 7 toward the liquid crystal display element 1 in a direction within a predetermined angle range with respect to the normal line direction of the liquid crystal display element 1. It is an optical element that can transmit light and limit the transmission of light in a direction inclined at an angle other than the predetermined angle range with respect to the normal direction. The viewing angle limiting element 10 includes a first retardation plate that gives a half-wave phase difference to transmitted light and a second retardation plate that gives a half-wave phase difference to transmitted light. ing. In the first retardation plate, a plurality of first retardation layers having a predetermined planar shape are arranged at an interval on a plane in a region corresponding to the screen region of the liquid crystal display element. A plurality of second retardation plates are arranged in correspondence with regions other than the regions corresponding to the plurality of first retardation layers in the region corresponding to the pixel region. The first retardation plate and the second retardation plate are arranged with a predetermined gap between them.

  3 and 4 are a sectional view and a perspective view of a part of the viewing angle limiting element 10. This viewing angle limiting element 10 is provided with a first transparent plate 11 provided with a plurality of first ½ retardation layers 13 and a plurality of ½ retardation layers 14, and the first transparent plate The second transparent plate 12 is opposed to the plate 11 with a predetermined gap, and the polarizing film 15 is formed on one outer surface of the first and second transparent plates 11 and 12. A plurality of 1's having a predetermined planar shape are provided on the inner surface of the first transparent plate 11 facing the second transparent plate 12 by giving a half-wave phase difference between ordinary light and extraordinary light of transmitted light. / 2 The phase difference layer 13 is arrange | positioned at intervals planarly. A plurality of second ½ retardation layers 14 are arranged on the inner surface of the second transparent plate 12 so as not to face the plurality of first ½ retardation layers 13. . That is, as shown in FIG. 3, the plurality of ½ retardation layers 13 and 14 of the viewing angle limiting element 10 are alternately provided on the first transparent plate 11 and the second transparent plate 12. Observed from the normal direction of the liquid crystal display element, it substantially acts as one phase plate.

  The first transparent plate 11 and the second transparent plate 12 of the viewing angle limiting element 10 are each made of a glass plate or the like that hardly exhibits birefringence with respect to transmitted light.

  In this embodiment, the 1/2 retardation layers 13 and 14 are made of a uniaxially stretched film, a polymer liquid crystal layer, or the like, and the 1/2 retardation layers 13 and 14 are respectively determined in advance. It is formed in a stripe shape along the direction.

  The 1/2 retardation layers 13 and 14 may be, for example, a plurality of 1/2 retardation films obtained by cutting the uniaxially stretched film into a strip shape on the transparent plates 11 and 12 in a stripe shape. Alternatively, a polymer liquid crystal is applied or printed on the surfaces of the transparent plates 11 and 12, and the polymer liquid crystal is aligned in a stripe shape so that the molecular long axes are aligned in one predetermined direction to be polymerized. Can be formed.

  The ½ retardation layers 13 and 14 are formed in parallel so as to be separated by the same interval as the width thereof, and when viewed from the normal direction of the transparent plates 11 and 12, The side edges of the adjacent first retardation layer 13 and the side edge of the second retardation layer 14 are formed so as to coincide with each other.

  Further, the ½ retardation layers 13 and 14 are the same as the first retardation layer 13 and the first retardation layer 13 when viewed from the direction inclined in the width direction of the stripe with respect to the normal direction of the transparent plates 11 and 12. In order to obscure the parallel stripe pattern due to the overlapping of the side edges of the two retardation layers 14, the width corresponding to the plurality of pixels of the liquid crystal display element 1, preferably the width of one pixel. Are formed with the smallest possible width and spacing.

  The distance between the first and second transparent plates 11 and 12 is set in advance according to the viewing angle that restricts visual recognition, and is joined by a frame-shaped spacer 16 having a thickness corresponding to this distance. The spacer is configured so that the first and second light beams are incident on a range of a viewing restriction angle other than a predetermined viewing angle range between the first retardation layer and the second retardation layer. And a region having no retardation existing between the first retardation layers and a region having no retardation existing between the retardation layers of the second transparent plate 12. Each has a thickness corresponding to the length for transmission.

  That is, the distance between the first and second transparent plates 11 and 12 is, for example, when the visual recognition from a direction inclined at an angle larger than 45 ° with respect to the normal line of the liquid crystal display element 1 is limited. As in the embodiment, the interval between the first and second transparent plates 11 and 12 is set so that the interval between the ½ phase difference layer 13 and the ½ phase difference layer 14 is the same as the width and interval thereof. Set as follows. In addition, when the visible viewing angle is set to an angle range smaller than 45 °, the interval between the ½ retardation layer 13 and the ½ retardation layer 14 is set to the ½ retardation layers 13, 14. Set larger than the width and interval. On the other hand, when the viewing angle that is visible is set to an angle range larger than 45 °, the interval between the 1/2 phase difference layer 13 and the 1/2 phase difference layer 14 is smaller than the width and the interval. You only have to set it.

  Further, these transparent plates 11 and 12 may be provided so as to be able to come into contact with and separate from each other in a state of facing each other with a gap therebetween and a state of closely contacting each other.

  In this case, of the first and second transparent plates 11 and 12, the first transparent plate 11 has sufficient strength, and the second transparent plate 12 has elasticity to bend and deform in the thickness direction. In the peripheral portion, the transparent plates 11 and 12 are joined in an airtight state via a frame-like spacer 16 that defines the interval between the transparent plates 11 and 12.

  The viewing angle limiting element 10 sucks the air in the sealed space surrounded by the spacer 16 between the first and second transparent plates 11 and 12 to the outside of the space. The opposing distance variable device 17 is provided for bringing the transparent plates 11 and 12 into close contact with each other.

  FIG. 5 is a configuration diagram of the facing distance varying device 17, FIG. 5 (a) shows a state in which the first and second transparent plates 11 and 12 are separated, and FIG. 5 (b) shows the first and second. The transparent plates 11 and 12 are in close contact with each other.

  The facing distance varying device 17 is arranged outside the first and second transparent plates 11 and 12 along one edge thereof, and one end of which is provided in part of the frame-shaped spacer 16. A cylinder 18 connected to the hole, a piston 19 provided in the cylinder 18 so as to be movable in its length direction, a motor 20, and disposed at the other end of the cylinder 18 and driven to rotate by the motor 20. A reel 21, a wire 22 wound around the reel 21, introduced from a hole provided in the other end surface of the cylinder 18, and connected at its tip to the piston 19; and the other end of the cylinder 18 A brake mechanism 23 is disposed between the reel 21 and locks the wire 22, and a protective cover 24.

  When the first and second transparent plates 11, 12 are brought into close contact with each other, the facing distance varying device 17 rotates the reel 21 in the wire winding direction by the motor 20 and moves the piston 19 by the wire 22. The cylinder 18 is moved from one end side to the other end side, and the air in the space between the transparent plates 11 and 12 is sucked into the cylinder 18. Thereby, the inside of the space is set to a negative pressure with respect to the outside air pressure, and the second transparent plate 12 is bent and deformed by the pressure difference to be brought into close contact with the first transparent plate 11. The motor 20 is stopped when a predetermined amount of air necessary to bring the first and second transparent plates 11 and 12 into close contact with each other, and the brake mechanism 23 as shown in FIG. The wire 22 is locked to keep the transparent plates 11 and 12 in close contact.

  Further, the facing distance varying device 17 releases the lock of the wire 22 by the brake mechanism 23 when the first and second transparent plates 11 and 12 are separated from each other. When the lock of the wire 22 is released, the second transparent plate 12 is restored to the state facing the first transparent plate 11 with the space due to its elasticity, and accordingly, the air in the cylinder 18 is restored. Is pulled between the transparent plates 11 and 12, and the piston 19 rotates the reel 21 in the wire feeding direction and returns to one end side of the cylinder 18 as shown in FIG.

  The rotating shaft of the motor 20 is substantially in a no-load state when the motor 20 is stopped (when there is no driving force). Therefore, the reel 21 is restored by the restoring force due to the elasticity of the second transparent plate 12. Can be rotated in the wire feeding direction to separate the first and second transparent plates 11 and 12 from each other.

  FIG. 6 is a configuration diagram of another opposing distance varying device 17, and this opposing distance varying device 17 is arranged on the outer side of the first and second transparent plates 11 and 12 along one edge thereof. The cylinder 25 has one end connected to an intake hole provided in a part of the frame-shaped spacer 16 and a screw on the outer periphery, and one end is provided on the other end surface of the cylinder 25 in the cylinder 25. A rotary shaft 26 is provided in parallel with the cylinder shaft so as to protrude from the hole, and the protrusion is connected to a reversible rotary motor 27 disposed on the other end side of the cylinder 25, and the rotary shaft 26 in the cylinder 25. And a piston 28 that is prevented from rotating in the circumferential direction by the cylinder 25 and is moved in the length direction of the cylinder 25 by the rotation of the rotating shaft 26, and the rotating shaft 26 is locked. Brake mechanism 9, is made from the protective cover 24.

  When the first and second transparent plates 11 and 12 are brought into close contact with each other, the facing distance varying device 17 rotates the rotating shaft 26 in one direction by the motor 27 so that the piston 28 is connected to one end of the cylinder 25. The air in the space between the transparent plates 11 and 12 is sucked into the cylinder 25 by moving from the side to the other end side. Thereby, the inside of the space is set to a negative pressure with respect to the outside air pressure, and the second transparent plate 12 is bent and deformed by the pressure difference to be brought into close contact with the first transparent plate 11. The motor 27 is stopped when a predetermined amount of air necessary to bring the first and second transparent plates 11 and 12 into close contact with each other, and the rotating shaft 26 is locked by the brake mechanism 29. The contact state of the transparent plates 11 and 12 is maintained.

  Further, when the first and second transparent plates 11 and 12 are separated from each other, the facing distance varying device 17 releases the lock of the rotating shaft 26 by the brake mechanism 29 and the motor 27 causes the rotating shaft to move. 26 is rotated in the reverse direction, the piston 28 is moved in the reverse direction, and the air in the cylinder 25 is forcibly returned between the transparent plates 11 and 12, whereby the second transparent plate 12 is moved by the air pressure. The first transparent plate 11 is restored to a state facing the first transparent plate 11 with the interval. When the piston 28 is moved to the initial position on one end side of the cylinder 25, that is, when the second transparent plate 12 is restored, the motor 27 is stopped and the rotating shaft 26 is moved by the brake mechanism 29. It locks and the separated state of the said transparent plates 11 and 12 is hold | maintained.

  The liquid crystal display device is mounted on a display unit of an electronic device such as a mobile phone, and the facing distance varying device 17 has, for example, a wide viewing angle by a viewing angle selection key provided on the electronic device. The distance between the first and second transparent plates 11 and 12 is changed according to the selection of the narrow viewing angle. Specifically, the first and second transparent plates 11 and 12 are brought into close contact when a wide viewing angle is selected, and the first and second transparent plates 11 and 12 are selected when a narrow viewing angle is selected. Are separated from each other.

  As shown in FIG. 1, the polarizing film 15 of the viewing angle limiting element 10 is attached to the outer surface of the first transparent plate 11 among the first and second transparent plates 11 and 12. The polarizing film 15 is arranged so that the transmission axis 15a thereof is substantially orthogonal to the transmission axis 6a of the polarizing plate 6 on the opposite side to the observation side of the pair of polarizing plates 5 and 6 of the liquid crystal display element 1. Is done.

  And the slow axis 13a of the 1/2 phase difference layer (henceforth a 1st phase difference layer) 13 formed in the 1st transparent plate 11 of the said viewing angle limiting element 10, and the said 2nd transparent plate The slow axes 14a of the ½ retardation layer (hereinafter referred to as the second retardation layer) 14 formed on 12 are substantially parallel to each other and substantially with respect to the transmission axis 15a of the polarizing film 15. Cross at an angle of 45 °.

  In this embodiment, the slow axes 13a and 14a of the first retardation layer 13 and the second retardation layer 14 are respectively in the longitudinal direction of the retardation layers 13 and 14 formed in a stripe shape, that is, The liquid crystal display element 1 is made to coincide with a direction substantially orthogonal to the horizontal axis 100 of the screen.

  The viewing angle limiting element 10 is disposed between the liquid crystal display element 1 and the surface light source 7 with the polarizing film 15 facing the surface light source 7.

  In this liquid crystal display device, since the viewing angle limiting element 10 is disposed between the liquid crystal display element 1 and the surface light source 7, among the illumination light from the surface light source 7, the method of the liquid crystal display element 1 is used. The direction of the visual field limit range that transmits light directed in the direction of the visual field range that is visible within a predetermined angle range with respect to the line direction and restricts visual recognition outside the predetermined angle range with respect to the normal direction. By blocking the light traveling toward, it is possible to perform a narrow security viewing angle display with a high degree of security without the possibility of someone looking into the display from an oblique direction.

  FIG. 7 is an operation explanatory diagram showing the polarization state of transmitted light when the first and second transparent plates 11 and 12 of the viewing angle limiting element 10 face each other with a gap therebetween. Illumination light (unpolarized light) from the surface light source 7 is transmitted to the viewing angle limiting element 10 by the polarizing film 15 on the incident side of the viewing angle limiting element 10 (surface facing the surface light source 7). It enters as linearly polarized light P parallel to the axis 15a.

  Then, the half retardation layers 13 and 14 on the inner surfaces of the first and second transparent plates 11 and 12 of the viewing angle limiting element 10 are located in regions between the retardation layers 13 of the first transparent plate 11. Each retardation layer 14 of the second transparent plate is formed to face each other, and the interval between the ½ retardation layer 13 and the ½ retardation layer 14 is substantially equal to the width and interval thereof. . Further, the slow axis 13 a of the first retardation layer 13 formed on the first transparent plate 11 of the viewing angle limiting element 10 and the second retardation layer formed on the second transparent plate 12. The 14 slow axes 14 a are substantially parallel to each other and intersect the transmission axis 15 a of the polarizing film 15 at an angle of substantially 45 °.

  Therefore, out of the linearly polarized light P incident on the viewing angle limiting element 10, the 1/2 phase difference layer 13 of the first transparent plate 11 and the 1/2 transparent plate 12 of the first transparent plate 12 of the viewing angle limiting element 10. The light transmitted through one of the phase difference layers 14 is rotated by 90 ° by either one of the ½ phase difference layers 13, 14, and the polarization plane with respect to the linearly polarized light P transmitted through the polarizing film 15. Becomes linearly polarized light S orthogonal to each other and is emitted from the viewing angle limiting element 10. On the other hand, of the linearly polarized light P incident on the viewing angle limiting element 10, the 1/2 phase difference layer 13 of the first transparent plate 11 of the viewing angle limiting element 10 and the 1/2 position of the second transparent plate 12. The light transmitted through both of the phase difference layers 14 has a plane of polarization rotated by 180 ° by the respective half phase difference layers 13, 14, and is a straight line having a plane of polarization parallel to the linearly polarized light P transmitted through the polarizing film 15. The polarized light P is emitted from the viewing angle limiting element 10. In addition, the polarization plane of light that does not pass through either the ½ retardation layer 13 of the first transparent plate 11 or the ½ retardation layer 14 of the second transparent plate 12 of the viewing angle limiting element 10 is rotated. Instead, the linearly polarized light P is emitted from the viewing angle limiting element 10 as it is.

  Therefore, out of the light traveling in the direction of the visual field range within a predetermined angle range with respect to the normal direction of the liquid crystal display element 1, the 1/2 phase difference layer 13 of the first transparent plate 11 and the first phase difference layer 13. The phase difference layer existing between the phase difference layers of the second transparent plate 12 or the phase difference layer existing between the phase difference layers of the first transparent plate 11 Light passing through the half phase difference layer 14 of the transparent plate 12 (hereinafter referred to as viewing angle light L1) is incident on the liquid crystal display element 1 as linearly polarized light S whose polarization plane is rotated by 90 °. Since the plane of polarization of the linearly polarized light S is substantially parallel to the transmission axis 6 a of the opposite side polarizing plate 6, the linearly polarized light S passes through the liquid crystal display element 1 and is observed by an observer.

  And among the light which goes to the direction of the visual field range within a predetermined angle range with respect to the normal direction of the liquid crystal display element 1, the 1/2 phase difference layer 13 of the first transparent plate 11 and the first phase difference layer 13. The light L2 transmitted through both of the retardation layers of the second transparent plate 12 and the phase difference layer existing between the retardation layers of the first transparent plate 11 and the retardation layer of the second transparent plate 12 Light L3 that passes through a region having no phase difference between them and does not pass through both of the two phase difference layers enters the liquid crystal display element 1 as linearly polarized light P. Since the plane of polarization of the linearly polarized light P is substantially orthogonal to the transmission axis 6a of the opposite-side polarizing plate 6, it is absorbed by the opposite-side polarizing plate 6 and is not emitted to the observation side.

  Further, a visual field that restricts visual recognition tilted at an angle larger than the predetermined angle range in a direction intersecting the length direction of the ½ retardation layers 13, 14 with respect to the normal direction of the liquid crystal display element 1. Light traveling in the direction of the limit range (hereinafter referred to as viewing limit angle light L2 and L3) passes through the ½ retardation layers 13 and 14 of both the first and second transparent plates 11 and 12, or The first and second transparent plates 11 and 12 pass through a region having no phase difference between the phase difference layers 13 and 13 and a region having no phase difference between 14 and 14. Accordingly, the viewing angle limit light L2 and L3 is rotated by 90 ° on the plane of polarization by the ½ phase difference layer 13 of the first transparent plate 11, and the ½ phase difference of the second transparent plate 12 is obtained. The polarization plane is further rotated by 90 ° by the layer 14, or the polarization state is changed between the retardation layers 13, 13 and 14, 14 of the first and second transparent plates 11, 12. Without being transmitted as linearly polarized light P.

  Since the plane of polarization of the linearly polarized light P is substantially orthogonal to the transmission axis 6a of the opposite-side polarizing plate 6, it is absorbed by the opposite-side polarizing plate 6 and is not emitted to the observation side.

  Therefore, when the first and second transparent plates 11 and 12 of the viewing angle limiting element 10 are arranged with a space therebetween, only the viewing angle light L1 is as shown by the arrow in FIG. The light passes through the liquid crystal display element 1 and is emitted within a range of a small divergence angle θ1 (45 ° in this embodiment) having a predetermined angle range on the observation side. Therefore, the display of the liquid crystal display element 1 can be seen from the direction of the angle range with respect to the normal line of the liquid crystal display element 1, that is, from the front direction. In this case, the half retardation layer 13 of the first transparent plate 11 among the light traveling in the direction of the visual field range within a predetermined angle range with respect to the normal direction of the liquid crystal display element 1. And the light transmitted through both of the phase difference layers of the second transparent plate 12 and the region having no phase difference existing between the phase difference layers of the first transparent plate 11 and the phase difference layer of the second transparent plate 12 Since the light transmitted through the region having no phase difference between the two is absorbed by the opposite polarizing plate 6, the viewing angle light L1 has the strongest light intensity in the front direction, and is inclined with respect to the normal line. As a result, the light intensity decreases. When viewed from the direction of the field-of-view restriction range inclined at a larger angle from the front direction of the liquid crystal display element 1, the entire screen becomes black.

  Thus, in this liquid crystal display device, the transmission axis 15a of the polarizing film 15 of the viewing angle limiting element 10 is substantially equal to the transmission axis 6a of the polarizing plate 6 on the side opposite to the observation side of the liquid crystal display element 1. The slow axes 13a of the ½ retardation layers 13 of the first transparent plate 11 of the viewing angle limiting element 10 and the ½ retardation layers 14 of the second transparent plate 12 are orthogonal to each other. The slow axis 14a is substantially parallel to each other, and the slow axes 13a, 14a of the ½ retardation layers 13, 14 are substantially 45 ° with respect to the transmission axis 15a of the polarizing film 15. Since they intersect at an angle, it is possible to perform a narrow viewing angle display in which the entire screen is black when viewed from an oblique direction.

  In addition, the liquid crystal display device has a stripe shape in which the half retardation layers 13 and 14 on the inner surfaces of the first and second transparent plates 11 and 12 of the viewing angle limiting element 10 are arranged in a predetermined direction. Therefore, the viewing angle in the direction intersecting with the length direction of the stripe-like 1/2 phase difference layers 13 and 14 can be narrowed.

  In addition, the liquid crystal display device includes a plurality of ½ retardation layers 13 and 14 on the opposing inner surfaces of the first and second transparent plates 11 and 12 that are opposed to each other with a space therebetween. Each retardation layer 14 of the second transparent plate 12 is formed to face each other between the retardation layers 13 of the plate 11, and a polarizing film 15 is formed on one outer surface of the first and second transparent plates 11, 12. Narrow viewing angle display is performed by the viewing angle limiting element 10 provided with. Therefore, since the viewing angle limiting element 10 has a simple structure and can be easily manufactured, the cost of the liquid crystal display device can be reduced.

  In this liquid crystal display device, the half retardation layers 13 and 14 on the inner surfaces of the first and second transparent plates 11 and 12 of the viewing angle limiting element 10 are formed in a simple stripe shape. Therefore, the viewing angle limiting element 10 can be further easily manufactured, and the cost of the liquid crystal display device can be further reduced.

  Furthermore, in this liquid crystal display device, the first and second transparent plates 11 and 12 of the viewing angle limiting element 10 are provided so as to be able to come into contact with and separate from each other in a state of facing each other and a state of being in close contact with each other. Thus, the narrow viewing angle display and the wide viewing angle display that allows the display to be viewed from an oblique direction can be performed.

  FIG. 8 is an operation explanatory view showing the polarization state of transmitted light when the first and second transparent plates 11 and 12 of the viewing angle limiting element 10 are brought into close contact with each other. At this time, since the half phase difference layers 13 and 14 on the inner surfaces of the first and second transparent plates 11 and 12 are continuously arranged on the same surface, the viewing angle light L11 is also the viewing limit angle light. L12 and L13 also pass through only one of the 1/2 phase difference layers 13 and 14 of the first and second transparent plates 11 and 12 of the viewing angle limiting element 10.

  Therefore, at this time, both the viewing angle light L11 and the viewing angle limiting light L12 and L13 have a plane of polarization with respect to the linearly polarized light P incident on the viewing angle limiting element 10 through the incident side polarizing film 15. The linearly polarized light S rotated by 90 ° is emitted to the liquid crystal display element 1, and these lights L 11, L 12, and L 13 are incident on the liquid crystal display element 1 through the opposite polarizing plate 6.

  Therefore, when the first and second transparent plates 11 and 12 of the viewing angle limiting element 10 are brought into close contact with each other, the viewing angle light L11 and the viewing limiting angle lights L12 and L13 are transmitted through the liquid crystal display element 1. The liquid crystal display element 1 itself emits light with a spread angle corresponding to the viewing angle characteristic of the liquid crystal display element 1 itself, so that the display of the liquid crystal display element 1 is also normal to the liquid crystal display element 1 from the front direction. It can also be seen from a direction inclined with respect to the direction.

  FIG. 9 is an intensity distribution diagram of the emitted light when the liquid crystal display device performs narrow viewing angle display. FIG. 9A illustrates the light intensity distribution in a direction parallel to the horizontal direction of the screen of the liquid crystal display element 1. FIG. 9B shows a light intensity distribution in a direction parallel to the vertical direction of the screen. FIG. 10 is an intensity distribution diagram of the emitted light when the liquid crystal display device performs wide viewing angle display. FIG. 10A shows the light intensity in a direction parallel to the horizontal direction of the screen of the liquid crystal display element 1. FIG. 10B shows a light intensity distribution in a direction parallel to the vertical direction of the screen. In these figures, the light intensity ratios are shown by taking the intensity of outgoing light in the front direction when the wide viewing angle display shown in FIG.

  9A and 10A, the positive angle is the tilt angle in the right direction of the screen with respect to the normal direction (0 ° direction) of the liquid crystal display element 1, and the negative angle is It is the tilt angle of the left direction of the screen with respect to the normal direction. Further, in FIGS. 9B and 10B, a positive angle is an upward tilt angle of the screen with respect to the normal direction, and a negative angle is a lower angle of the screen with respect to the normal direction. The tilt angle of the direction.

  In the narrow viewing angle display of the liquid crystal display device, the emitted light has a light spread angle range of 50% or more in the left-right direction of the screen, and the normal direction of the liquid crystal display element 1 as shown in FIG. 9A. In the range of ± 12 ° to 17 °, the spread angle range of the light having an intensity ratio of 50% or more in the vertical direction of the screen is ± 20 ° to the normal direction as shown in FIG. 9B. The light is in the range of 22 °. Therefore, the viewing angle in the left-right direction of the screen (the direction intersecting the length direction of the striped phase difference layers 13 and 14 of the viewing angle limiting element 10) can be sufficiently narrowed.

  In addition, the emitted light when the liquid crystal display device performs wide viewing angle display has a spread angle range of light having an intensity ratio of 50% or more in the left-right direction of the screen, as shown in FIG. 10A. In the range of ± 23 ° to 25 ° with respect to the line direction, the spread angle range of the light having an intensity ratio of 50% or more in the vertical direction of the screen is ± 20 with respect to the normal direction as shown in FIG. 10B. It is light in the range of ° to 22 °. Therefore, the viewing angles in the horizontal direction and vertical direction of the screen can be sufficiently widened.

  The viewing angle limiting element 10 of the first embodiment is joined to the first and second transparent plates 11 and 12 through a frame spacer 16 in an airtight state. , 12 is provided with a facing distance variable device 17 that sucks the air in the sealed space surrounded by the spacer 16 between the first and second transparent plates 11 and 12 by sucking the air inside the space. However, the viewing angle limiting element 10 may have another configuration.

Embodiment 2. FIG.
FIG. 11 is a cross-sectional view of a part of a viewing angle limiting element 10 showing a second embodiment of the present invention. This viewing angle limiting element 10 is sufficient for both the first and second transparent plates 11 and 12. The first transparent plate 11 and the second transparent plate 12 are formed of a glass plate having strength and the like, and the opposed distance variable device 30 having a configuration different from the opposed distance variable device 17 of the first embodiment is used. It is designed to come in contact. A plurality of ½ retardation layers 13 and 14 formed on the inner surfaces of the first and second transparent plates 11 and 12 facing each other, and one outer surface of the first and second transparent plates 11 and 12, respectively. The polarizing film 15 provided in is the same as in the first embodiment.

  The facing distance varying device 30 of the viewing angle limiting element 10 includes a pair of reinforcing frames 31 and 32 fixed to the peripheral portions of the first and second transparent plates 11 and 12, respectively, and the reinforcing frames 31 and 32. Are inserted into holes (not shown) provided opposite to each other, and a flange portion 33a provided at one end is brought into contact with the outer surface of one reinforcing frame 31, and the other end side of the other reinforcing frame 32 is provided. A rod 33 protruding from the outer surface, a wedge member abutting portion 33b formed at a right angle to the rod 33 at the other end of the rod 33, and the pair of reinforcements fitted to the rod 33 A spring member (coil spring) 34 provided between the frames 31 and 32 and a wedge member 35 slidably provided on the outer surface of the other reinforcing frame 32 are provided.

  The wedge member 35 has two horizontal surfaces (surfaces parallel to the outer surface of the reinforcing frame 33) 35a, which are different in height, on one end side and the other end side of the surface opposite to the surface in sliding contact with the outer surface of the reinforcing frame 32. 35b is formed, and an inclined surface 35c connecting the two horizontal surfaces 35a and 35b is formed between them. The difference in height between the two horizontal surfaces 35a and 35b is the first and second transparent plates 11. , 12 is set to be the same as the interval between the transparent plates 11, 12 when they are separated from each other.

  The wedge member 35 has a position where a low horizontal surface 35a on one end side contacts the wedge member contact portion 33b of the rod 33, and a high horizontal surface 35b on the other end side contacts the wedge member contact portion 33b of the rod 33. It is slidably provided at a position in contact with the.

  The rod 33, the spring member 34, and the wedge member 35 are provided at a plurality of locations, for example, at four corners of the reinforcing frames 31, 32, and the wedge member 35 at each location is at one end side. Are arranged in the same direction, and the wedge members 35 at the respective positions are arranged on the same side with respect to the wedge member abutting portion 33b of the rod 33, and one end side of each wedge member 35 is arranged in the same direction. And fixed to a frame-like member (not shown) provided on the outer surface of the other reinforcing frame 32 so as to be able to reciprocate in the sliding direction of the wedge member 35 so as to be integrally slid by the movement of the frame-like member. ing.

  That is, the facing distance varying device 30 is configured such that the wedge member 35 is slid to a position where a low horizontal surface 35a on one end side thereof abuts against a wedge member abutting portion 33b of the rod 33, whereby the spring of the spring member 34 is moved. The first and second transparent plates 11 and 12 are separated by a force so as to face each other with a gap therebetween, and the wedge member 35 has a high horizontal surface 35b on the other end side. The first and second transparent plates 11 and 12 are brought into close contact with each other by being slid to a position in contact with 33b.

  In the liquid crystal display device of this embodiment, a slide knob for selecting a wide viewing angle and a narrow viewing angle is provided in an electronic device such as a mobile phone in which the liquid crystal display device is mounted, and by sliding operation of the slide knob, It is preferable to move the frame-like member to which the wedge members 35 of the respective portions of the facing distance varying device 30 are fixed, and in this way, the viewing angle limiting element 10 can be used without using electric power. The first and second transparent plates 11 and 12 can be brought into contact with and separated from each other.

  Note that the viewing angle limiting element 10 of the above embodiment is formed by forming the 1/2 phase difference layers 13 and 14 of the first and second transparent plates 11 and 12 in a stripe shape. The phase difference layers 13 and 14 may be formed in other shapes, for example, a checkered pattern.

  Further, the liquid crystal display device of the above embodiment includes the normally white mode liquid crystal display element 1, but the liquid crystal display element 1 may be of a normally black mode. Further, not limited to the TN type, STN (super twisted nematic) type, a vertical alignment type in which liquid crystal molecules are aligned substantially perpendicular to the substrate surface, and substantially to the substrate surface without twisting the liquid crystal molecules. The liquid crystal display element may be either a horizontal alignment type aligned in parallel with the liquid crystal or a bend alignment type in which liquid crystal molecules are bend aligned. Further, for example, comb-shaped first and second electrodes for forming a plurality of pixels are provided on the inner surface of one of a ferroelectric or antiferroelectric liquid crystal display element and a pair of substrates, and a horizontal line is provided between these electrodes. A lateral electric field control type that changes the alignment state of liquid crystal molecules by generating an electric field (electric field in a direction along the substrate surface) may be used.

  Further, the liquid crystal display element 1 has a liquid crystal layer made of a liquid crystal to which a dichroic dye is added, and a polarizing plate for increasing the contrast is arranged on either the observation side or the opposite side. Guest host) type liquid crystal display element. In the case of a GH type liquid crystal display element in which a polarizing plate is arranged on the side opposite to the observation side, the transmission axis 15a of the polarizing film 15 of the viewing angle limiting element 10 is substantially the same as the transmission axis of the polarizing plate of the GH liquid crystal display element. In the case of a GH type liquid crystal display element in which a polarizing plate is arranged on the observation side, the transmission axis 15a of the polarizing film 15 of the viewing angle limiting element 10 is substantially the same as the transmission axis of the polarizing plate of the GH liquid crystal display element. By making them parallel to each other, it is possible to perform a narrow viewing angle display in which the entire screen is black when viewed from an oblique direction.

  In the liquid crystal display device of the above embodiment, the liquid crystal display element 1 is a color image display element provided with three color filters of red, green, and blue respectively corresponding to a plurality of pixels. The invention can also be applied to a field sequential liquid crystal display device using a liquid crystal display element that does not include a color filter.

1 is an exploded perspective view of a liquid crystal display device showing a first embodiment of the present invention. The side view of the said liquid crystal display device. Sectional drawing of a part of viewing angle limiting element. The perspective view of a part of the viewing angle limiting element. Operation | movement explanatory drawing of the state which separated the 1st and 2nd transparent plate, and the state which contact | adhered the said 1st and 2nd transparent plate which shows the structure of the facing distance variable apparatus of the said viewing angle limiting element. The block diagram of another opposing distance variable apparatus. Operation | movement explanatory drawing which shows the polarization | polarized-light state of the transmitted light when the 1st and 2nd transparent plate of the said viewing angle restriction | limiting element has opposed with the space | interval. Operation | movement explanatory drawing which shows the polarization state of the transmitted light when the 1st and 2nd transparent plate of the said viewing angle restriction | limiting element is stuck. The light intensity distribution figure of the direction parallel to the left-right direction of the screen of a liquid crystal display element and the direction parallel to the up-down direction of the said screen which shows intensity distribution of the emitted light at the time of narrow viewing angle display of the said liquid crystal display device. The light intensity distribution figure of the direction parallel to the left-right direction of the screen of a liquid crystal display element and the direction parallel to the up-down direction of the said screen which shows intensity distribution of the emitted light at the time of wide viewing angle display of the said liquid crystal display device. Sectional drawing of a part of viewing angle limiting element which shows 2nd Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element, 5 and 6 ... Polarizing plate, 5a, 6a ... Transmission axis, 7 ... Surface light source, 10 ... Viewing angle limiting element, 11, 12 ... Phase difference plate, 11a, 12a ... Transparent plate, 13, 14 ... 1/2 phase difference layer, 13a, 14a ... slow axis, 16 ... polarizing film, 16a ... transmission axis, 17, 30 ... retardation plate contacting / separating means.

Claims (12)

A liquid crystal display element having a liquid crystal layer and a first polarizing plate ;
A surface light source for irradiating the liquid crystal layer with light through the first polarizing plate ;
A viewing angle limiting element disposed between the first polarizing plate and the surface light source ;
With
The viewing angle limiting element is:
A first substrate and a second substrate which are arranged so as to face each other and the facing distance is variable,
The first substrate is disposed on the surface facing the second substrate so as to protrude from the facing surface toward the second substrate, and gives a phase difference of ½ wavelength to the transmitted light. 1 retardation layer;
The second substrate is disposed on the surface facing the first substrate so as to protrude from the facing surface toward the first substrate, and gives a phase difference of ½ wavelength to the transmitted light. Two retardation layers;
A second polarizing plate disposed so that a transmission axis is orthogonal to the transmission axis of the first polarizing plate;
With
The second substrate is disposed between the first substrate and the second polarizing plate,
The second polarizing plate is disposed between the second substrate and the surface light source,
The liquid crystal display device , wherein the first retardation layer and the second retardation layer are alternately arranged when viewed in plan from a predetermined direction . The liquid crystal display device according to claim 1, further comprising a control unit that controls the facing distance between the first substrate and the second substrate . When the viewing angle limiting element is controlled so that the facing distance between the first substrate and the second substrate is the closest, the first retardation layer becomes the second substrate. The liquid crystal display device according to claim 2, wherein the second retardation layer is in contact with the first substrate and is in contact with the first substrate . 4. The liquid crystal display device according to claim 3, wherein a protruding height of the first retardation layer from the facing surface is equal to a protruding height of the second retardation layer from the facing surface . The first retardation layer is configured such that a slow axis of the first retardation layer is parallel to a slow axis of the second retardation layer and transmitted through the second polarizing plate. 5. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is disposed at an angle of 45 ° with respect to the axis . 6. The liquid crystal display according to claim 1, wherein the first retardation layer and the second retardation layer are arranged so that a planar shape thereof is a stripe pattern. 6. apparatus. The liquid crystal display device according to claim 6, wherein the first retardation layer has a stripe width equal to a gap width between stripes . The liquid crystal display device according to claim 6, wherein a stripe width of the first retardation layer is equal to a stripe width of the second retardation layer . The surface light source is
A light guide plate disposed parallel to the second polarizing plate;
A light emitting element that makes light incident from an end face parallel to the extending direction of the stripe pattern among the end faces of the light guide plate;
The liquid crystal display device according to claim 6, further comprising: The viewing angle limiting element is configured so that the first retardation layer is in contact with the second substrate and the second retardation layer is in contact with the first substrate. The retardation layer is variably formed in a second state in which the retardation layer is not in contact with the second substrate and the second retardation layer is in contact with the first substrate. The liquid crystal display device according to claim 1 . 11. The liquid crystal display device according to claim 10, wherein the viewing angle limiting element is formed to be variable from the second state to the first state . A liquid crystal display element having a liquid crystal layer and a first polarizing plate;
A surface light source for irradiating the liquid crystal layer with light through the first polarizing plate;
A viewing angle limiting element disposed between the first polarizing plate and the surface light source;
With
The viewing angle limiting element is:
A first substrate and a second substrate which are arranged so as to face each other and the facing distance is variable,
A first retardation layer disposed on a surface of the first substrate facing the second substrate so as to protrude from the facing surface toward the second substrate;
A second retardation layer disposed on a surface of the second substrate facing the first substrate so as to protrude from the facing surface toward the first substrate;
A second polarizing plate disposed so that a transmission axis is orthogonal to the transmission axis of the first polarizing plate;
With
The second substrate is disposed between the first substrate and the second polarizing plate,
The second polarizing plate is disposed between the second substrate and the surface light source,
The first retardation layer is configured such that a slow axis of the first retardation layer is parallel to a slow axis of the second retardation layer and transmitted through the second polarizing plate. Arranged at an angle of 45 ° to the axis,
The liquid crystal display device , wherein the first retardation layer and the second retardation layer are alternately arranged when viewed in plan from a predetermined direction .

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