JP4899503B2 - Display device - Google Patents

Description

  The present invention relates to an optical element and a display device capable of controlling the direction of light emitted from an image display element such as a liquid crystal display element.

  Liquid crystal displays (LCDs) are used for small and medium-sized displays such as mobile phones, personal digital assistants (PDAs), and notebook personal computers as well as large flat panel displays of 32 inches or more. It has been.

  The liquid crystal display includes a liquid crystal display element in which a liquid crystal material is sealed between a pair of transparent substrates. Conventionally, the TN (Twisted Nematic) method, in which the alignment direction of the liquid crystal is twisted by 90 ° between the upper and lower substrates, has been the mainstream as a liquid crystal driving method, but it has poor visibility when viewed obliquely and has a narrow viewing angle. There was a problem.

  In recent years, methods such as IPS (In Plane Switching-mode), PVA (Patterned Vertical Alignment), and MVA (Multi-domain Vertical Alignment) have been developed as methods for solving this problem. Color shift and contrast are greatly improved. Recently, the usage of enjoying still images and moving images on mobile phones and PDAs has increased, and the opportunity to view one monitor in addition to individuals has increased. Against this background, the above-described viewing angle expansion technology has begun to be applied to mobile displays such as mobile phones.

  On the other hand, if the viewing angle is too wide, there is a problem in that display information on the screen is recognized by surrounding people in a train or the like. Thus, a film that limits the viewing angle by being attached to a liquid crystal display screen is known. This film is made of a louver film having a black stripe pattern, and controls the direction of emitted light to prevent the screen from being viewed from an oblique direction. However, since the film fixes the light emission direction, it is not possible to switch the viewing angle according to the situation.

  On the other hand, technologies capable of arbitrarily switching the viewing angle are described in, for example, Patent Documents 1 to 4 below. Patent Document 1 discloses a liquid crystal display device that can adjust the viewing angle by controlling the luminance of the backlight and the degree of scattering of the emitted light. In Patent Document 2, a TN liquid crystal cell for display is arranged between a polymer dispersion type liquid crystal cell and a guest-host type liquid crystal cell, thereby enabling switching between a reflective type and a transmissive type and a switching of a viewing angle. Technology is disclosed. Patent Document 3 discloses a liquid crystal display in which an optical compensation layer is disposed in front of a display liquid crystal cell, and the viewing angle is switched by electrically controlling the phase difference amount of the optical compensation layer. Is disclosed.

  On the other hand, in Patent Document 4, as shown in FIG. 18, first and second regions 101 and 102 are respectively formed between a pair of transparent base materials 103 and 104, and the transmittance of the second region 102 is obtained. A configuration of the viewing angle control element 100 is disclosed in which the transmittance of the second region 102 is switchable so that is smaller than the transmittance of the first region 101. This viewing angle control element 100 is disposed on the front side (observer side) of the liquid crystal display panel, and narrow-angle mode (FIG. 18A) that emits light L emitted from the light source 105 and transmitted through the liquid crystal display panel at an angle θ1. The wide viewing angle mode (FIG. 18B) in which the light L is emitted at an angle θ2 is selectively configured to be taken.

  Here, the second region 102 is composed of a guest-host type liquid crystal or polymer dispersed type liquid crystal containing a dichroic dye. In a state where no electric field exists between the pair of transparent base materials 103 and 104, the transmittance of the second region 102 is smaller than the transmittance of the first region 101, and the light L incident on the second region 102 is transmitted. Narrow viewing angle mode that limits the exit angle by absorbing or scattering the light. On the other hand, when a predetermined electric field is formed between the pair of transparent base materials 103 and 104, the liquid crystal material in the second region 102 is aligned in the vertical direction and exhibits high transmittance. And a wide viewing angle mode that transmits not only the light L incident on the second region 102 but also the light L incident on the second region 102.

  The first and second regions 101 and 102 are formed in an area facing each pixel of the display panel. Specifically, as shown in FIG. 19A, one first region 101 is arranged corresponding to each pixel region of RGB (red, green, and blue), or the first region 101 for each pixel as shown in FIG. 19B. The formation pitch of the first and second regions 101 and 102 is defined such that a plurality of regions 101 are arranged. The formation width of the first region 101 is equal to the formation width of the second region 102 or smaller than the formation width of the second region 102.

JP-A-9-105907 Japanese Patent Laid-Open No. 10-197844 JP 2005-309020 A JP 2005-221756 A

  However, the configuration described in Patent Document 1 is disadvantageous in terms of low power consumption because it is necessary to increase the luminance of the backlight in the wide viewing angle mode (when the degree of scattering of the emitted light is large). . In the configuration of Patent Document 2, since three liquid crystal cells are required, it is difficult to reduce the cost and the thickness is increased. Furthermore, in the configuration of Patent Document 3, it is difficult to manufacture the substrate at low cost because an alignment process is required, and it is necessary to use a glass substrate. Therefore, a film substrate aimed at reducing the weight, reducing the thickness, and improving the impact resistance There is a problem that it is difficult to use.

  On the other hand, in the configuration of Patent Document 4, since the formation width of the first region 101 having high transmittance is equal to or less than the formation width of the second region 102 having low transmittance, the narrow viewing angle mode is used. There is a problem in that the amount of light is limited, leading to a decrease in luminance.

  In addition, since the first and second regions 101 and 102 having different transmittances are formed in the area where one pixel opposes, the light scattered in the low transmittance region leaks to the display pixels and adjacent cells. The display may blur, resulting in a decrease in sharpness or color shift. Furthermore, the alignment when placing the patterns of the first and second regions 101 and 102 formed in units of one pixel on the display pattern is very complicated in the process, and the image quality depends on the alignment accuracy. Also become.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a lightweight, thin, and low-cost optical element and display device that can control a light beam direction while suppressing a decrease in luminance.

  In solving the above-described problems, the optical element of the present invention includes a pair of transparent base materials, a first region made of a translucent material patterned between the pair of transparent base materials, and a first region. And a second region including a liquid crystal material that is selectively switched between a light-transmitting state and a scattering or absorption state, and the formation width of the first region is the formation width of the second region It is formed larger than.

  The optical element of the present invention is used, for example, as a light beam control element that adjusts the viewing angle of a liquid crystal display, and can electrically switch the viewing angle between wide and narrow depending on the light transmission state and the scattering or absorption state of the second region. To do. Specifically, it functions to widen the viewing angle when the second region is in a light-transmitting state and narrow the viewing angle when the second region is in a scattering or absorbing state.

  Therefore, in the present invention, by increasing the formation width of the first region as compared with the formation width of the second region, the luminance in the front direction is increased particularly in the narrow viewing angle mode, and the image is enhanced. Realized. Preferably, a high-quality image can be formed regardless of the alignment accuracy with respect to the image display element by making the formation pitch of the second region larger than the pixel pitch of the image display element.

  In addition, the optical element according to the present invention can be easily and inexpensively manufactured only by patterning the first and second regions between a pair of transparent substrates, and the transparent substrate is made of a plastic film or the like. As a result, it becomes possible to reduce the thickness and weight and improve the impact resistance.

  The composite material filled in the second region is preferably a polymer dispersed liquid crystal in which a liquid crystal material is dispersed in a polymer material or a material in which a dichroic black pigment is added to the polymer dispersed liquid crystal. The former can realize the light scattering state of the second region, and the latter can realize the light absorption state of the second region.

  However, the present invention is not limited to this, and the second region may be filled only with a liquid crystal material. In this case, power consumption can be reduced by providing a bistable structure in which a light scattering alignment state and a light transmission alignment state are maintained in an electric field.

  The translucent material can be processed into a desired shape by patterning a transparent photosensitive material. The pattern shape of the second region is determined by the pattern shape of the translucent material. Preferably, the pattern shape of the second region is a stripe shape or a lattice shape, but is not limited to this. Further, the translucent material can be patterned by a method other than the photolithography technique, and for example, a press method or mechanical processing is used. Moreover, you may make it form the said 2nd area | region by forming a translucent material with a transparent polymer film, and giving a groove process etc. on the said film.

  The optical element according to the present invention can be installed on the front side of the image display element. As the image display element, various panels such as a liquid crystal display, an organic EL (electroluminescence) display, a plasma display, a field emission display, and an electrophoretic display can be used.

  Moreover, when using a liquid crystal display element (liquid crystal display panel) as an image display element, the optical element which concerns on this invention can also be arrange | positioned between a liquid crystal display element and a surface emitting light source (backlight unit). In this case, the optical element is configured so that the second region can be selectively switched between the light-transmitting state and the light-scattering state, so that the viewing angle can be expanded by the light scattering function in the second region. It can also be given.

  As described above, according to the present invention, the optical element that controls the light direction of the display element and switches the viewing angle can be reduced in price, weight, and thickness, and deterioration in image quality due to a decrease in luminance can be suppressed.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a side sectional view showing a schematic configuration of a display device 10 according to a first embodiment of the present invention, where A shows a narrow viewing angle state and B shows a wide viewing angle state. The display device 10 of this embodiment mainly includes a backlight unit 1, a liquid crystal display element (liquid crystal display panel) 2, and a light beam control element 11.

  The backlight unit 1 is configured as a surface emitting light source disposed on the back side (lower side in the drawing) of the liquid crystal display element 2. The backlight unit 1 may be a direct backlight unit or an edge light backlight unit including a light guide plate. In addition to a linear light source such as a fluorescent tube, a point light source such as a light emitting diode (LED) is used as the light source. The backlight unit 1 is configured by appropriately combining the light source, a light diffusing sheet such as a diffusion plate or a diffusion sheet, and a brightness enhancement film having a light collecting property such as a prism sheet or a lens sheet. Can do.

  The liquid crystal display element 2 is configured as an image display element according to the present invention. The liquid crystal display element 2 is configured by enclosing a liquid crystal material between a pair of transparent substrates. The driving method of the liquid crystal display element 2 is not particularly limited, but in the present embodiment, an IPS method, an MVA method, or the like excellent in viewing angle characteristics is adopted. Further, polarizing plates are arranged on the front side (upper side in the drawing) and the back side of the liquid crystal display element 2 even if not shown.

  The light beam control element 11 is configured as an optical element according to the present invention. As will be described later, the light beam control element 11 has a function of controlling the direction of the light beam L emitted from the backlight unit 1 and passed through the liquid crystal display element 2, and the light beam direction is set at a certain angle as shown in FIG. 1A. A narrow viewing angle mode that limits the range and a wide viewing angle mode that expands the light ray direction to an angle range equal to or greater than the predetermined angle as shown in FIG. 1B can be switched.

  FIG. 2 is a perspective view showing a schematic configuration of the light beam control element 11. The light beam control element 11 includes a first region composed of a pair of upper and lower transparent substrates 12 and 13 and a translucent material 14 patterned between the pair of transparent substrates 12 and 13, and the first region. And a second region made of the composite material 15 including a liquid crystal material. Transparent electrode films 16 and 17 are formed on the inner surfaces of the pair of transparent base materials 12 and 13, respectively. A voltage source 18 and a switch 19 are connected to the transparent electrode films 16 and 17. The switch 19 corresponds to the “switching means” of the present invention.

  The composite material 15 is selectively switched between a light transmission state and a scattering or absorption state by ON / OFF of a voltage applied between the transparent electrode films 16 and 17. In this embodiment, as will be described later, the composite material 15 is composed of polymer dispersed liquid crystal (PDLC), and in a state where the voltage is OFF, the composite material 15 is in a light scattering orientation state in which incident light is scattered. In the ON state, a light transmissive alignment state that transmits incident light is obtained.

  Therefore, when the voltage is OFF, the light transmissive material 14 is surrounded by the scattering wall made of the composite material 15. For this reason, as shown in FIG. 1A, only the light that passes through the translucent material 14 out of the light L emitted from the liquid crystal display element 2 is emitted to the front side, and the light incident on the composite material 15 is scattered and not transmitted. . Thereby, the emission angle of the light L emitted from the liquid crystal display element 2 is limited to a predetermined angle range in the front direction (narrow viewing angle mode). Further, the light scattering property of the composite material 15 causes light incident on the composite material 15 to be scattered toward the translucent material 14, so that the luminance in the front direction can be improved.

  On the other hand, when the voltage is ON, the composite material 15 is in a transparent state, and as shown in FIG. 1B, the light emitted from the liquid crystal display element 2 passes through the light beam control element 11 with almost no change in the light beam direction (wide viewing angle). mode). If the liquid crystal display element 2 has a wide viewing angle, a viewing angle characteristic substantially equivalent to that of the liquid crystal display element 2 can be obtained.

  Next, details of the light beam control element 11 according to the present invention will be described.

  The transparent base materials 12 and 13 are made of a transparent film or sheet such as glass, plastic film, polymer film containing an inorganic filler, and in particular, a plastic film that is lightweight, can be thinned, and has excellent productivity, handleability, and impact resistance. (Polymer film) is preferred.

  The translucent material 14 forming the first region is not particularly limited as long as it is a material transparent to the light emitted from the liquid crystal display element 2. For example, PMMA (polymethyl methacrylate), PC (polycarbonate), UV A transparent resin material such as (ultraviolet) curable resin is used. In particular, the translucent material 14 is preferably made of a UV photosensitive resin capable of patterning the translucent material 14 using photolithography technology.

  Note that the light-transmitting material 14 can also be configured using a polymer material containing liquid crystal molecules. In this case, as the polymer material, a resin or a liquid crystal polymer that can be cured by ultraviolet rays or heat to restrain liquid crystal molecules is used. That is, as long as the director direction of the liquid crystal is not changed by voltage application, the light-transmitting material 14 can be configured using a polymer material containing liquid crystal molecules.

  As shown in FIG. 2, the translucent material 14 is patterned in a quadrangular prism shape. The pattern shape is not limited to this quadrangular shape, and may be a polygonal column shape such as a triangular column shape or a hexagonal column shape, a cylindrical shape, or other geometric shapes. In the example of FIG. 2, the rectangular columnar translucent materials 14 are arranged and arranged at equal pitches in the row and column directions, but it is not limited thereto.

  On the other hand, the composite material 15 forming the second region is formed of a polymer dispersed liquid crystal. The composite material 15 constitutes the second region in the form of vertical and horizontal stripes, that is, a lattice, so as to fill the space between the light-transmitting materials 14. The shape of the second region is determined by the shape of the translucent material 14. For example, if the translucent material 14 is a hexagonal column shape, the second region has a honeycomb shape.

  In the light control element 11 according to the present invention, the formation width W1 of the translucent material 14 (first region) is formed larger than the formation width W2 of the composite material 15 (second region). As the area of the translucent material 14 is larger, the amount of light transmitted through the translucent material 14 is increased, thereby improving the straightness of the light beam and improving the front luminance and reducing the display blur.

  The light beam control element 11 is formed such that the formation pitch of the composite material 15 is larger than the pixel pitch of the liquid crystal display element 2. If the formation pitch of the composite material 15 is about the same as the pixel pitch, moire fringes or display unevenness occurs due to misalignment between the liquid crystal display element 2 and the light beam control element 11. That is, by making the pattern pitch of the composite material 15 larger than the pixel pitch, the light control element 11 can be easily incorporated into the liquid crystal display element 2 and the image quality can be improved by suppressing the occurrence of moire and display unevenness. Will be able to.

From a geometrical relationship, when the pitch of the pattern of the composite material 15 is p, the width is w, and the height is h, the viewing angle φ is φ = 2 tan ⁻¹ {(p−w) / h}. In order to obtain the same narrow viewing angle, the height h must be increased as the pattern pitch p of the composite material 15 increases. For example, when the narrow viewing angle is 60 °, when the pattern width of the composite material 15 is 10 μm to 30 μm, the pattern having a height of 300 μm and a pitch of 200 μm, a height of 150 μm and a pitch of 100 μm, or a height of about 75 μm and a pitch of about 50 μm. A combination is preferred, but not limited to this. The pattern width of the composite material 15 can be selected from both the aperture ratio and the optical characteristics, but is preferably about 5 μm or more and 100 μm or less. More preferably, they are 10 micrometers or more and 50 micrometers or less, More preferably, they are 15 micrometers or more and 30 micrometers or less.

  When the intended narrow viewing angle and the narrowing of the pattern width of the composite material 15 are compatible, the aspect ratio of the pattern shape of the composite material 15 becomes high. For this reason, in the configuration in which the transparent electrode films 16 and 17 for driving the liquid crystal of the composite material 15 are formed on the inner surfaces of the transparent base materials 12 and 13, the applied voltage increases as the height of the composite material 15 increases. . Therefore, as shown in FIG. 4, the liquid crystal in the composite material 15 is driven without increasing the applied voltage by forming transparent electrode films 16 and 17 on both side walls of the translucent material 14 sandwiching the composite material 15. And power consumption can be reduced.

  Note that the pattern pitch of the composite material 15 is not limited to be constant, and the composite material 15 may be patterned by changing the pattern pitch regularly or irregularly. The pitch, width and height of the pattern of the composite material 15 can be appropriately selected according to the size of the viewing angle to be switched.

  The polymer-dispersed liquid crystal constituting the composite material 15 is made of a material in which liquid crystal droplets 5 are filled in the dispersed voids in the polymer film 4 as schematically shown in FIG. At this time, the refractive index of the polymer film 4 is preferably matched with the ordinary light refractive index of the droplet 5. In the state of no electric field, the orientation of the droplets 5 is random as shown in FIG. 3, and the refractive index of the polymer film 4 and the refractive index of the droplets 5 do not match. Scattered. Thereby, the composite material 15 is in a state of scattering incident light. On the other hand, when a predetermined electric field is applied to the composite material 15, the molecular long axes of the droplets 5 are aligned in the electric field direction, and the composite material 15 becomes a medium having a uniform refractive index. For this reason, the composite material 15 takes a translucent state in which incident light is transmitted without being scattered.

  In addition to the above configuration, the composite material 15 can be formed of, for example, a liquid crystal material alone, a porous material filled with the liquid crystal material, a dispersion liquid in which fine particles are dispersed in the liquid crystal material, or the like. As the fine particles, polymer fine particles such as acrylic, glass fine particles and the like can be used. In this case, it is desirable that the refractive index of the fine particles is equal to the ordinary light refractive index of the liquid crystal.

  As the liquid crystal molecules constituting the composite material 15, known nematic liquid crystal, cholesteric liquid crystal, smectic liquid crystal, and the like can be used. The liquid crystal material does not have to have a normal refractive index that matches the refractive index of the translucent material 14, but preferably matches to improve the transmittance.

  As the transparent electrode films 16 and 17, conductive polymer materials can be used in addition to transparent conductive oxides such as ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), and ZnO. The transparent electrode films 16 and 17 may be solid films or a lattice pattern film corresponding to the second region filled with the composite material 15. A DC power source, an AC power source, or a pulse power source can be used as the voltage source 18 that applies a predetermined voltage between the transparent electrode films 16 and 17.

  The switch 19 may be either electrically opened or closed or mechanically opened or closed. The switch 19 can be installed in the casing of the display device 1 and can be switched by the operator. When the display device 1 is used as a monitor of, for example, a mobile phone or a notebook personal computer, the switch 19 can be configured as the monitor periphery, the vicinity of the key operation unit, or a part thereof.

  Next, a method for manufacturing the light beam control element 11 of the present embodiment configured as described above will be described. FIG. 5 is a process cross-sectional view illustrating a method for manufacturing the light beam control element 11.

  First, the transparent substrate 13 on one side having the transparent electrode film 17 formed on the surface is prepared (FIG. 5A). Next, a layer made of a transparent polymer material constituting the translucent material 14 is formed on the transparent electrode film 17 (FIG. 5B). As this transparent polymer material, a UV photosensitive resin material is used. As this type of photosensitive material, a general positive resist or negative resist can be used, and a sheet-like dry film resist can be used in addition to a solution resist. In particular, a chemically amplified resist capable of high aspect processing (for example, “SU-8” manufactured by Kayaku Microchem Corporation) is preferable.

  Next, the transparent polymer material layer is subjected to exposure and phenomenon processing to form a second region 15A filled with the composite material 15 in a later step (FIG. 5C). At this time, the formation width W1 of the translucent material 14 (first region) is formed larger than the formation width W2 of the composite material 15 (second region). The formation pitch of the composite material 15 is formed larger than the pixel pitch of the liquid crystal display element 2.

  Subsequently, the transparent substrate 12 on the other side having the transparent electrode film 16 formed on the surface is prepared, and this is bonded to the transparent substrate 13 on the one side (FIG. 5D). Thus, a cell substrate in which the translucent material 14 is sandwiched between the pair of transparent electrode films 16 and 17 is configured. At this time, the translucent material 14 functions as a spacer that regulates the gap between the pair of transparent base materials 12 and 13. Finally, by filling the second region 15A between the pair of transparent base materials 12 and 13 with the composite material 15, the light control element 11 having the above-described configuration is manufactured (FIG. 5E).

  The display device 10 of the present embodiment configured as described above includes the light beam control element 11 that can be electrically switched between the wide viewing angle mode and the narrow viewing angle mode. By switching to the viewing angle mode, it is possible to view a large number of images simultaneously on a single monitor, and by switching the light beam control element 11 to the narrow viewing angle mode, display information on the screen in a train or the like can be obtained. It is possible to prevent peeping from people around you.

  Further, in the light beam control element 11 of the present embodiment, since the formation width of the translucent material 14 is formed larger than the formation width of the composite material 15, the luminance in the front direction is increased particularly in the narrow viewing angle mode. Thus, a high-definition image can be provided.

  Further, since the pattern pitch of the composite material 15 is formed larger than the pixel pitch of the liquid crystal display element 2, the light control element 11 can be easily incorporated into the liquid crystal display element 2, and moire and display unevenness can be generated. The image quality can be improved by suppressing the image quality.

Furthermore, since the light control element 11 can be easily manufactured using a photolithography technique, the light control element 11 that is lightweight, thin, and excellent in impact resistance can be manufactured at low cost with high productivity.
(Second Embodiment)

  6 and 7 are a side sectional view and a perspective view showing a schematic configuration of the display device 20 and the light beam control element 21 according to the second embodiment of the present invention. In the figure, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the light beam control element 21 of the present embodiment, the shape of the translucent material 14 formed as the first region between the pair of transparent base materials 12 and 13 is different from that of the first embodiment described above. That is, in this example, the translucent material 14 is formed in the shape of a quadrangular pyramid whose area on the bottom surface side is larger than that on the upper surface side, and the side wall surface in contact with the composite material 15 is a tapered surface.

  Similarly, in the present embodiment, the formation width W1 of the translucent material 14 (first region) is formed larger than the formation width W2 of the composite material 15 (second region). The formation pitch of the composite material 15 is formed larger than the pixel pitch of the liquid crystal display element 2.

  In the light beam control element 21 configured as described above, it is possible to obtain the same operations and effects as in the first embodiment. In particular, according to the present embodiment, since the upper surface of the translucent material 14 is formed smaller in area than the bottom surface, the emission angle of the transmitted light L can be made smaller than that in the first embodiment. Therefore, it is possible to limit the light beam direction and narrow the viewing angle without reducing the formation width of the translucent material 14.

  FIG. 8 is a process cross-sectional view illustrating an example of a method for forming the light transmissive material 14 in the light beam control element 21 having the above configuration.

  First, a layer of a transparent polymer material constituting the translucent material 14 is formed on the lower transparent substrate 13 having the transparent electrode film 17 formed on the surface (FIG. 8A). Next, in order to form a second region 15A filled with the composite material 15 in a later step, a transparent polymer material layer is used by using a press die 22 having a mold surface to transfer and form the second region 15A. 14 is press-molded (FIG. 8B). Thereby, a plurality of translucent materials 14 having a quadrangular pyramid shape are formed, and at the same time, a second region 15A having a lattice pattern is formed between the translucent materials 14 (FIG. 8C). Thereafter, in the same manner as in FIG. 5, after the upper transparent base material is bonded together, the light beam control element 21 is manufactured by filling the composite material.

  In the present embodiment, the mold surface of the press die 22 is configured such that the side surface of the translucent material 14 is formed in a tapered shape, and therefore, the mold release property is relatively excellent. In order to further improve the releasability of the press die 22, it is preferable to coat the die surface with a release agent or release it while applying ultrasonic waves. As the die press method, a method such as a heat press, a UV press, and an imprint can be used. In addition to machining, a mold obtained by electroforming a resist pattern processed by photolithography can be used for manufacturing the mold.

  In contrast to the above, it is also possible to form the light-transmitting material so that the upper surface side is larger in area than the bottom surface side. In this case, after the translucent material 14 having the above-described configuration is produced on the upper transparent substrate 12 by the same method as described above, the transparent substrate 13 on the lower side is turned upside down by turning the transparent substrate 12 upside down. And laminated. By making the upper surface side of the translucent material 14 larger in area than the bottom surface side, the outgoing angle of the transmitted light can be made larger than that in the first embodiment.

(Third embodiment)
FIG. 9 is a side sectional view showing a schematic configuration of the display device 30 and the light beam control element 31 according to the third embodiment of the present invention. In the figure, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, the configuration of the composite material 35 that switches the direction of the outgoing light of the liquid crystal display element 2 in the light control element 31 is different from that in the first embodiment described above, and the composite material 35 is dichroic in the polymer dispersed liquid crystal. It is composed of a material to which a black pigment is added.

  Similarly, in the present embodiment, the formation width W1 of the translucent material 14 (first region) is formed larger than the formation width W2 of the composite material 35 (second region). The formation pitch of the composite material 35 is formed larger than the pixel pitch of the liquid crystal display element 2.

  When a dichroic black pigment is added to the polymer-dispersed liquid crystal, it becomes black when no voltage is applied and becomes transparent when a voltage is applied. Therefore, the second region filled with the composite material 35 becomes black when no voltage is applied, and the light incident on the region is absorbed and the viewing angle is narrowed as shown in FIG. 9A. On the other hand, in the voltage application state, as shown in FIG. 9B, the composite material 35 becomes transparent and is expanded to a viewing angle equivalent to the viewing angle characteristic of the liquid crystal display element 2.

  As described above, in the light beam control element 31 of this embodiment, the light beam direction is controlled by switching between absorption / transparency by using a material obtained by adding a dichroic black pigment to a polymer dispersed liquid crystal as the composite material 35. Like to do. Accordingly, the luminance tends to be lower than the configuration in which the light beam direction is controlled by switching between scattering / transparency by the composite material 15 composed only of the polymer dispersed liquid crystal as in the first embodiment. It is possible to improve the contrast.

(Fourth embodiment)
FIG. 10 is a process cross-sectional view illustrating the configuration and one manufacturing method of the light beam control element 41 according to the fourth embodiment of the present invention.

  In the present embodiment, in the light beam control element 41, the translucent material 44 is composed of a transparent plastic film shown in FIG. 10A. 10B, a groove 45A is formed on the surface of the plastic film 44, and the groove 45 is configured as a “second region” in which the composite material 45 is filled. Next, as shown in FIG. 10C, the groove 45A on the plastic film 44 is filled with a composite material 45 made of polymer dispersed liquid crystal by, for example, a screen printing method or the like. Finally, the plastic film 44 is sandwiched between the pair of transparent base materials 12 and 13 having the transparent electrode films 16 and 17, and the light beam control element 41 shown in FIG. 10D is manufactured.

  According to this embodiment, since the translucent material 44 can be formed by a roll-to-roll method by using a film substrate, the light beam control element 41 can be manufactured at low cost and with high productivity. If the pattern formation of the composite material 45 including liquid crystal and the bonding process of the transparent base materials 12 and 13 are also performed by the roll-to-roll method, the light control element 41 can be manufactured at a lower cost and with higher productivity. It can be manufactured.

  In addition, as a formation method of the groove | channel 45A with respect to the plastic film 44, the method of directly heat-pressing a board | substrate and the groove processing method using a cutting tool with a very thin blade edge | tip are applicable. Further, a glass substrate can be used instead of the plastic film. As a method for forming a groove on the glass substrate, wet etching with hydrofluoric acid, dry etching, laser ablation, or the like is preferable.

  Similarly, in the present embodiment, the formation width W1 of the translucent material 44 (first region) is formed larger than the formation width W2 of the composite material 45 (second region). The formation pitch of the composite material 45 is formed larger than the pixel pitch of the liquid crystal display element 2.

(Fifth embodiment)
11 and 12 are process diagrams illustrating a method for manufacturing a light beam control element according to the fifth embodiment of the present invention. In the figure, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, a light beam control element is manufactured by patterning a translucent material and a composite material using a composite material containing liquid crystal as a starting material. As shown in FIG. 11, a layer made of a UV curable composite material 57 in which liquid crystal molecules are dispersed in an ultraviolet curable polymer is formed on the transparent substrate 13, and the space between the upper and lower transparent substrates 12 and 13 is formed. In a state where a predetermined voltage is applied, UV irradiation is performed through a mask 52. In the UV curable composite material 57, the region of the mask 52 facing the light transmitting portion 52a is cured by UV irradiation, and the orientation of the liquid crystal is restricted in the electric field direction. On the other hand, the region corresponding to the lattice-shaped light shielding pattern 53 of the mask 52 is switched between the transparent state and the scattering state by turning on / off the electric field without restricting the orientation of the liquid crystal.

  As described above, in the UV curable composite material 57, the region irradiated with UV is configured as a translucent material portion 54 that maintains a transparent state regardless of the presence or absence of an electric field. Conversely, the region not irradiated with UV is configured as a composite material portion 55 that can be switched to a transparent / scattering state depending on the presence or absence of an external electric field.

  According to the present embodiment, the light beam control element can be manufactured without performing the phenomenon processing on the translucent material or the filling process of the composite material, so that the cost and productivity are low compared with the first embodiment described above. A light control element can be manufactured with high.

  FIG. 12 is a process diagram illustrating a modification of this embodiment. In this example, as the exposure mask 52, a mask provided with a semi-translucent portion 53a between the translucent portion 52a and the light shielding portion 53 is used. By using such a mask 52, the amount of irradiation of UV transmitted through the semi-transparent portion 53a is lower than that of UV transmitted through the transparent portion 52. Therefore, the region of the UV curable composite material layer 57 corresponding to the semi-translucent portion 53 a is configured as a second composite material portion 56 having intermediate characteristics between the translucent material portion 54 and the composite material portion 55.

  The second composite material portion 56 is switched to a transparent state in the voltage application state in the same manner as the first composite material portion 55, but functions as an optical region having translucency and scattering properties in an electric field state. . Further, the second composite material portion 56 is switched to a transparent state at a voltage lower than that of the first composite material portion 55. Therefore, in this example, in addition to the narrow viewing angle mode and the wide viewing angle mode, it is possible to set a viewing angle mode between these modes.

(Sixth embodiment)
FIG. 13 is a side sectional view showing a schematic configuration of a light beam control element 61 according to the sixth embodiment of the present invention. In the figure, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the first embodiment described above, the viewing angle mode is controlled by electrically switching between the light scattering state and the light transmission state of the composite material composed of the polymer dispersed liquid crystal. However, since a wide viewing angle mode is obtained by applying an electric field to make the composite material 15 transparent, in principle, a wide viewing angle mode is obtained compared to a case where a narrow viewing angle mode is obtained in the absence of an electric field. In the mode, power consumption is large.

  Therefore, an increase in power consumption can be suppressed by adding to the light beam control element the ability to maintain a transparent state even after voltage interruption. Specifically, the capacitance of the composite material portion is increased, or the applied pulse interval is increased. Furthermore, there is a method in which a periodic structure such as a fine grating is formed on the substrate surface, and the alignment state of the liquid crystal is maintained even after the electric field is removed.

  The light beam control element 61 shown in FIG. 13 includes a pair of transparent base materials 12 and 13, a translucent material 64 patterned between the pair of transparent base materials 12 and 13, and a translucent material 64. And a liquid crystal material 65 that is arranged and selectively switched between a light-transmitting state and a scattering state. In the present embodiment, the liquid crystal material 65 is made of a liquid crystal material, and the liquid crystal material 65 has a light-scattering alignment distribution shown in FIG. 13A and a light-transmitting alignment distribution shown in FIG. It is configured to take a state.

  As in the example shown in the figure, the entire area of the liquid crystal material 65 can be dispersed on the surface of the light control element 61 by distributing and arranging the area occupied by the liquid crystal material 65 within the area occupied by the light transmissive material 64. Become. Thereby, the interaction of alignment between liquid crystals can be greatly reduced, a bistable state can be easily realized, and the retention of each stable state can be enhanced. In order to maintain a bistable state, a necessary alignment treatment may be performed on the boundary surface between the translucent material 64 and the liquid crystal material 65.

  In FIG. 13A, the liquid crystal material 65 has a light scattering orientation distribution, and exhibits a light scattering function with respect to incident light due to a difference in refractive index from the light transmitting material 64. At this time, by making the formation width of the translucent material 64 larger than the formation width of the liquid crystal material 65 as illustrated, only the light incident on the translucent material 64 is transmitted and the light incident on the composite material 65 is transmitted. Regulates transmission of light. Thereby, the light beam control element 61 takes a narrow viewing angle mode. On the other hand, in FIG. 13B, the liquid crystal material 65 has a light-transmitting alignment distribution, and a wide viewing angle mode is obtained by exhibiting a light transmission function with respect to incident light. Switching between the narrow viewing angle mode and the wide viewing angle mode can be realized by a non-continuous closing operation of the switch 19, and after switching the mode, the mode can be maintained even if the switch 19 is opened.

(Seventh embodiment)
FIG. 14 is a side sectional view showing a schematic configuration of a display device 70 according to a seventh embodiment of the present invention. In the figure, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the display device 70 according to the present embodiment, the light beam control element 11 is disposed between the backlight unit 1 and the liquid crystal display element 2. The light beam control element 11 has a function of controlling the incident angle of light incident on the liquid crystal display element 2 from the backlight unit 1.

  The light beam control element 11 regulates the transmission by scattering the light incident on the composite material 15 out of the light L emitted from the backlight 1 in a no-electric field state in which the composite material 15 is in a light scattering orientation state. To do. As a result, only the light in the front direction that passes through the translucent material 14 is incident on the liquid crystal display element 2, so that the display device 70 takes the narrow viewing angle mode shown in FIG. 14A.

  On the other hand, when a predetermined voltage is applied between the pair of transparent electrode films 16 and 17 of the light control element 11, the composite material 15 takes a light-transmitting alignment state and emits light emitted from the backlight 1 without scattering. . Thereby, the light which permeate | transmits the translucent material 14 and the composite material 15 injects into the liquid crystal display element 2, and the display apparatus 70 will take the wide viewing angle mode shown to FIG. 14B.

  As described above, in this embodiment, the viewing angle characteristics of the display device 70 are switched by controlling the incident angle of the backlight light incident on the liquid crystal display element 2 by the light beam control element 11.

  By the way, in the light beam control element 11, the polymer-dispersed liquid crystal constituting the composite material 15 selects the size of the liquid crystal droplets and the thickness of the composite material 15, so that the degree of scattering and the scattering in the no-field alignment state are selected. The angle is controlled. That is, in the light beam control element 11 shown in FIG. 14, the backlight light incident on the composite material 15 is backscattered to restrict light emission, but the scattering mode is reduced by reducing the layer thickness of the composite material 15 or the like. And the viewing angle characteristics of the display device can be controlled by the scattered light.

  For example, the display device 70A shown in FIG. 15 includes a light beam control element 71 in which the layer of the composite material 15 is thinner than the above example. According to this example, the composite material 15 of the light beam control element 71 exhibits a forward scattering state in the light scattering orientation state shown in FIG. 15A, so that the backlight light is compared with the light transmission orientation state shown in FIG. 15B. L can be incident on the liquid crystal display element 2 at a wide angle. Therefore, the wide viewing angle mode is set in FIG. 15A and the narrow viewing angle mode is set in FIG. 15B.

  The light scattering angle in forward scattering can also be controlled by the pattern shape of the composite material 15. In the display device 70B and the display device 70C shown in FIGS. 16 and 17, the cross-sectional shape of the layer of the composite material 15 has a trapezoidal shape. In the example of FIG. 16, a light control element 72 is provided in which the pattern shape of the composite material 15 is smaller in area on the liquid crystal display element side than the backlight side. In the example of FIG. A light beam control element 73 having a larger area on the liquid crystal display element side than on the light side is provided.

  As shown in FIGS. 16A and 17A, the light beam control element 72 has a wider scattering angle than the light beam control element 73 in terms of the scattering angle of the backlight light L when the composite material 15 is in the light scattering orientation state. Therefore, it is possible to control the width of the viewing angle depending on the size of the area of the composite material 15 on the liquid crystal display element side. The viewing angle when the composite material 15 has a light-transmitting orientation distribution is substantially the same in any of the light control elements 72 and 73 as shown in FIGS. 16B and 17B.

  In any of the above examples, the formation width of the translucent material 14 (first region) is formed larger than the formation width of the composite material 15 (second region), and the formation pitch of the composite material 15 Is formed larger than the pixel pitch of the liquid crystal display element 2.

  As mentioned above, although each embodiment of this invention was described, of course, this invention is not limited to these, A various deformation | transformation is possible based on the technical idea of this invention.

  For example, in each of the above embodiments, a liquid crystal display using a liquid crystal display element as an image display element has been described as an example. However, the present invention is not limited to this, and an organic EL (electroluminescence) display, plasma display, field emission display, electric It can also be applied to other displays such as electrophoretic displays.

  In each of the above embodiments, the example in which the optical element according to the present invention is used as a light beam control element for viewing angle adjustment has been described. Widely applicable to. For example, in a direct-type backlight unit, a light source that enables adjustment of the luminance distribution by disposing a composite material layer containing liquid crystal at a position directly above the light source and disposing a translucent material layer at a position directly above the light source The optical element of the present invention can be applied to an apparatus.

  Further, although a polymer dispersed liquid crystal is used as a composite material constituting the optical element according to the present invention, the ratio (or composition) of the liquid crystal material to the polymer material of the composite material is varied within the plane of the light control element. It is also possible. By changing the liquid crystal / polymer composition in the plane, it is possible to partially create regions having different scattering and absorption characteristics. The liquid crystal / polymer composition need not be varied along a clear boundary line, and the composition may be gradually changed in a gradient manner.

  For example, in the case of polymer dispersed liquid crystal, if R = liquid crystal / polymer material (wt%), light scattering ability and driving voltage are low when R is about 50% to 80%, and R is 80% or more or 50% or less. However, the light scattering ability is small and the driving voltage tends to be large. That is, when no voltage is applied to the electrode of the light control element, there is a scattering region in the plane of the light control element, so that light in the oblique direction can be restricted and the viewing angle can be narrowed. On the other hand, when a voltage is applied, the entire surface becomes transparent, so that the light emitted from the liquid crystal display element hardly changes, so that the viewing angle characteristic can be maintained in a wide state.

  The composite material is not limited to the polymer-dispersed liquid crystal, and a material in which a porous material is filled with liquid crystal may be used. In this case, the optical characteristics of the composite material can be arbitrarily adjusted by the configuration of the porous material.

  For example, when the panel angle is increased and the viewing angle is effectively limited, from the viewpoint of increasing the scattering power of the scattering portion in a narrow viewing angle state and lowering the scattering power of the transparent portion, the porous shape of the scattering portion is reduced. It is desirable that the average pore size is larger than the average pore size of the transparent portion. The average pore size can be obtained from an observation image obtained by observing a porous structure with an optical microscope or an electron microscope. It is also possible to perform observation by using a resin porous material after washing the liquid crystal with a solvent or the like.

  When producing a structure having a different average pore size using a material containing an ultraviolet curable resin and liquid crystal, it is desirable that the parallelism of the UV irradiation light is high. In order to obtain a uniform structure in the thickness direction, it is desirable to perform UV irradiation while applying a voltage to the electrode on the substrate. By doing so, scattering of UV light during UV irradiation can be suppressed, so that the uniformity of the pore size in the thickness direction of the porous material can be improved. From the viewpoint of a tissue having a small average pore size (increasing scattering performance), it is desirable to irradiate UV light with as high an intensity as possible. 30 mW / cm 2 or more is desirable. Further, it is desirably 100 mW / cm 2 or more, more preferably 200 mW / cm 2. It is preferable to suppress the temperature rise of the irradiated portion irradiated with high intensity UV light. It is desirable to perform precise temperature control of the irradiation area using a water cooling stage, an air cooling fan, or the like.

It is a sectional side view which shows schematic structure of the display apparatus and light beam control element by the 1st Embodiment of this invention. It is a partially broken perspective view which shows schematic structure of the light beam control element of FIG. It is a schematic diagram explaining a polymer dispersion type liquid crystal. It is a sectional side view which shows the modification of a structure of the light beam control element of FIG. It is process sectional drawing explaining the manufacturing method of the light beam control element of FIG. It is a sectional side view which shows schematic structure of the display apparatus and light beam control element by the 2nd Embodiment of this invention. It is a partially broken perspective view which shows schematic structure of the light beam control element of FIG. FIG. 7 is a process cross-sectional view illustrating a method for manufacturing the light beam control element of FIG. 6. It is a sectional side view which shows schematic structure of the display apparatus and light beam control element by the 3rd Embodiment of this invention. It is 1 process sectional drawing explaining the manufacturing method of the light control element by the 4th Embodiment of this invention. It is a perspective view explaining 1 process of the manufacturing method of the light clear writing element by the 5th Embodiment of this invention. It is process sectional drawing explaining the modification of the manufacturing process shown in FIG. It is a sectional side view which shows schematic structure of the light beam control element by the 6th Embodiment of this invention. It is a sectional side view which shows schematic structure of the display apparatus by the 7th Embodiment of this invention. FIG. 15 is a side cross-sectional view illustrating a modified example of the configuration of the display device of FIG. FIG. 16 is a side cross-sectional view illustrating another modification of the configuration of the display device in FIG. 14. FIG. 17 is a side cross-sectional view showing still another modification example of the configuration of the display device of FIG. It is principal part sectional drawing which shows schematic structure of the light beam control element which concerns on a prior art. It is a schematic block diagram of the principal part of the light beam control element of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Backlight unit (surface emitting light source), 2 ... Liquid crystal display element (image display element) 10, 20, 30, 40, 50, 60, 70, 70A, 70B, 70C ... Display apparatus 11, 21, 31 , 41, 61, 71, 72, 73 ... light beam control element (optical element), 12, 13 ... transparent substrate, 14, 44, 54 ... translucent material (first region), 15, 35, 45, 55 ... Composite material (second region), 16, 17 ... Transparent electrode film, 18 ... Voltage source, 19 ... Switch (switching means), 22 ... Press mold, 52 ... Mask, L ... Backlight, W1 ... Transparent Formation width of optical material (first region), W2... Formation width of composite material (second region)

Claims (1)

A liquid crystal display element;
A surface emitting light source disposed on the back side of the liquid crystal display element ;
An optical element that is disposed on the front side of the liquid crystal display element and that controls the direction of light emitted from the surface-emitting light source and passed through the liquid crystal display element ;
Switching means ,
The optical element is
A pair of transparent substrates having a transparent electrode film; and a composite material layer in which liquid crystal molecules are dispersed in an ultraviolet curable polymer material and disposed between the pair of transparent substrates, the composite material layer Includes a light-transmitting first region in which the polymer material is cured in a state in which the liquid crystal molecules are aligned in a direction in which the pair of transparent substrates face each other, a light-transmitting alignment state, and light scattering properties. An alignment state that is electrically switchable, and a second region adjacent to the first region, wherein the formation width of the first region is larger than the formation width of the second region. And
The switching means is
By setting the liquid crystal material in the translucent alignment state, a first viewing angle mode in which light is emitted from the liquid crystal display element at a first angle, and the liquid crystal material in the light scattering alignment state. And a switch that selectively switches between a second viewing angle mode for emitting the light beam from the liquid crystal display element at a second angle smaller than the first angle .

Images