JP2007057979A - Viewing angle control display device and terminal, and viewing angle control display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a viewing angle control display device capable of enlarging a display screen at a low cost. <P>SOLUTION: A perpendicular dichroic pigment layer 6 as a light ray regulating element is arranged in front of light irradiation direction of a backlight 5 as a sheet-like light source that emits light two-dimensionally. Further, a transparent/scattering switching element 7 is arranged in front of the pigment layer 6. Further, a display panel 10 is arranged via a polarizing plate 8a in front of the transparent/scattering switching element 7 and, furthermore, the polarizing plate 8a is arranged in front of the display panel 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a viewing angle control display device, a terminal, and a method capable of changing a visibility angle range of an image of a display panel such as a liquid crystal display element.

  In recent years, a display device is required to have a secret protection function that prevents a person other than the person who is viewing the display device, that is, a person nearby. For example, in a financial terminal or the like known as ATM (Automated teller machine), it is necessary to touch a numeric button displayed on the display device and input a personal code, and this display device is visually recognized by others. Must be avoided. Similarly, a mobile phone or the like is required to have a function that can prevent incoming information from being viewed by others in the vicinity of the person. In addition, in PDA (Personal Digital Assistance) and notebook personal computers (hereinafter referred to as notebook PCs), when used in transportation such as trains, a function is also provided so that other people in the vicinity cannot see them. Is required.

  On the other hand, there is a need to visually recognize the display device by a plurality of people. For example, when a TV image is displayed on a screen by a mobile phone or the like, there are cases where it is desired to show it to a person nearby in addition to the owner of the mobile phone. In some cases, the data screen of the notebook PC may be viewed by a plurality of people.

  Accordingly, the display device includes a narrow-field mode in which highly confidential information is viewed by an individual and a wide-field mode in which highly public information is viewed by a plurality of persons. In PDAs, notebook PCs, and the like, there is a demand for a display device that can switch between these display modes.

  As a display device capable of switching between the narrow field mode and the wide field mode, there is one disclosed in Patent Document 1. In the display device disclosed in Patent Document 1, a light source, a first optical element, a liquid crystal display element, and a second optical element are arranged in this order. The directivity is enhanced (collimated) by the optical element, and the light entering the liquid crystal display element and emitted from the liquid crystal display element is electrically controlled by the second optical element to diffuse and straighten the light beam. The first optical element is arranged to increase the directivity of light from the light source, and specifically includes a linear louver film. On the other hand, the second optical element can be switched between a scattering state and a transparent state by a voltage. As the second optical element, there is a polymer dispersed liquid crystal (PDLC) in which a polymer is dispersed in a liquid crystal or a liquid crystal region is dispersed in a polymer as a support medium. .

  Next, the operation principle of this display device will be described. First, in the narrow field mode, the second optical element is placed in a transparent state. For this reason, the light from the light source enters the liquid crystal display element while maintaining high directivity by the first optical element. The liquid crystal display element creates a display image with a plurality of pixels, but the directivity of incident light is not significantly changed. For this reason, although a display image can be visually recognized by an observer in front of the display device, the display image does not reach an observer positioned obliquely from the front of the display device, and cannot be visually recognized.

  Next, in the wide field mode, the second optical element is placed in a scattering state. For this reason, the highly directional light obtained by the first optical element becomes scattered light by the second optical element. This scattered light becomes incident light of the liquid crystal display element. For this reason, not only an observer in front of the display device but also an observer positioned in an oblique direction with respect to the display device can visually recognize the display image.

JP-A-9-197405 (FIGS. 2 and 5) US Pat. No. 2,053,173 JP-A-6-59287 (FIG. 1)

  However, the conventional viewing angle control display device described above has the following problems. That is, in Patent Document 1, a louver is shown as the first optical element. Generally, a micro louver is commercially available as a louver that can be used in a viewing angle control display device. However, when the display screen is enlarged, the micro louver must be enlarged. This large micro louver is extremely expensive. This is due to the manufacturing method of the microlouver. For example, as shown in Patent Document 2, a plurality of transparent films and opaque layers are laminated and cut out in the normal direction of the laminated surface to produce a microlouver. For this reason, in order to produce a large microlouver, an extremely large laminated block must be created, which is not practical.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a viewing angle control display device and a terminal capable of increasing the size of a display screen at low cost.

  The viewing angle control display device according to the present invention is a surface light source that emits light two-dimensionally, a light beam restricting element that restricts a light ray direction of the light from the surface light source, and the passage of light from the light ray restricting element. A transparent / scattering switching element for switching between a transparent state and a scattering state, and a display panel for generating an image upon incidence of light from the surface light source, the light beam regulating element or the transparent / scattering switching element, The light regulating element includes a dye layer oriented in the normal direction of the substrate surface.

  The viewing angle control display device preferably further includes an optical compensation layer that corrects obliquely incident light into linearly polarized light.

  Further, it is preferable that the display panel is a liquid crystal display panel, and a polarizing plate whose transmission axis extends in the vertical direction of the display screen is disposed on the light incident side of the liquid crystal display panel.

  Furthermore, it is preferable that the display panel is disposed on the light exit side of the transparent / scattering switching element, or the display panel is disposed between the surface light source and the light beam restricting element.

  A terminal according to the present invention includes any one of the above-described viewing angle control display devices.

  Further, in the viewing angle control display method according to the present invention, the light ray direction from the surface light source is regulated by a light ray regulating element having a dye layer oriented in the normal direction of the substrate surface, and the light from the light ray regulating element is controlled. The transparent / scattering switching element is switched between the transparent state and the scattering state with respect to the passage, and the visibility angle range of the image generated on the display panel is switched.

  In the present invention, a display device having a variable visibility angle range can be realized by using a dye layer in which light restricting elements are arranged. Since the arranged dye layers can be easily formed on a large substrate, a large viewing angle control display device can be manufactured at low cost. Further, by arranging the arranged dye layers on the surface light source and the display panel, it is possible to create a film capable of preventing peeping while fixing the visibility angle range. Since this arranged dye layer can be similarly formed on a large substrate, it can be manufactured at low cost.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. First, the viewing angle control display apparatus of 1st Embodiment of this invention is demonstrated with reference to FIG. In the present embodiment, a vertical dichroic dye layer 6 as a light restricting element is disposed in front of the light irradiation direction of the backlight 5 as a planar light source that emits light two-dimensionally. A transparent / scattering switching element 7 is disposed in front of the dye layer 6, and a display panel 10 is disposed in front of the transparent / scattering switching element 7 via a polarizing plate 8 a, and in front of the display panel 10. Further, a polarizing plate 8b is disposed.

  The transparent / scattering switching element 7 can switch between a transparent state and a scattering state by applying or not applying a voltage. The transparent / scattering switching element 7 includes, for example, a guest / host liquid crystal disclosed in Patent Document 3 and a PDLC (Polymer Dispersed Liquid Crystal) disclosed in Patent Document 1. In the case of guest-host liquid crystal, liquid crystal molecules and dichroic dye molecules are contained in a liquid crystal material sandwiched between two transparent substrates, and through a transparent electrode provided on the transparent substrate. When no voltage is applied, the optical axis (long axis) of the dichroic dye molecule is substantially parallel to the surface of the transparent substrate. On the other hand, when a voltage is applied between the transparent electrodes, the dichroic dye molecule rises perpendicular to the substrate surface, and light having an optical axis other than the optical axis of the dichroic dye molecule is It is absorbed by the molecule and does not pass through the guest / host liquid crystal. Thereby, the wide viewing angle and the narrow viewing angle can be switched by the presence or absence of voltage application to the guest-host liquid crystal or the voltage adjustment. In the case of PDLC, a liquid crystal layer sandwiched between a pair of transparent substrates is a liquid crystal region dispersed in a polymer support medium, and a voltage is applied to a transparent electrode provided on the transparent substrate. In PD, the PDLC becomes transparent, and in a state where no voltage is applied, the PDLC enters a scattering state. In this way, in any switching element 7, the viewing angle range can be switched between the wide viewing angle and the narrow viewing angle.

  The display panel 10 is, for example, a transmissive liquid crystal display element, but a transflective liquid crystal display element or the like can also be used.

  The polarizing plate 8a is a polarizing plate whose transmission axis extends in the vertical direction of the display screen. The polarizing plate 8b has a transmission axis extending in the left-right direction of the display screen. In FIG. 1, the characters “left”, “right”, “up”, and “bottom” are written for the light emitted from the output side polarizing plate 8b. Show. The direction parallel to the transmission axis 9 of the incident-side polarizing plate 8a is the left-right direction of the display screen, and the vertical direction is the vertical direction of the display screen. In order to display the information to be concealed on the display screen, it is necessary to block the light beam in the left-right direction.

  Next, the dichroic dye layer 8 as a light beam restricting element will be described. Hereinafter, the case where a uniaxial dichroic dye is used will be described, but the same effect can be obtained with respect to a dye or the like exhibiting biaxiality. The dichroic dye 1 is represented by a liquid crystal-like ellipsoid as shown in FIG. As shown in FIG. 2, polarized light that vibrates in the long axis direction of the dichroic dye 1 is strongly absorbed, and polarized light that vibrates in the short axis direction shows weak absorption.

  The optical properties when the dichroic dyes 1 as described above are arranged perpendicular to the incident surface will be described with reference to FIG. When non-polarized light 2 with no polarization polarization is incident, neither polarization of light incident in the direction perpendicular to the incident surface is absorbed. On the other hand, the light incident obliquely has the polarization in the vibration direction perpendicular to the incident surface as S-polarized light 3 and the polarization in the vibration direction parallel to the incident surface as P-polarized light 4. Then, as shown in FIG. 3A, the P-polarized light 4 is absorbed when obliquely incident. On the other hand, even when obliquely incident, the absorption of the S-polarized light 3 does not increase. For this reason, the obliquely emitted light from the vertically aligned dichroic dye 1 is biased to increase the S-polarized component. Therefore, the emitted light from the vertically aligned dichroic dye layer 6 disposed on the backlight 5 is in a state where there is a polarization deviation as shown in FIG.

  Next, with reference to FIG. 7, the production method of the vertical alignment dichroic dye layer 6 is demonstrated. First, as shown in FIG. 7A, an alignment film 16 that brings the liquid crystal into vertical alignment is applied on the substrate 17, and then the alignment film 16 is baked. Thereafter, a coating film composed of the dichroic dye 1 and the liquid crystalline monomer 14 is formed on the alignment film 16. Further, this coating film is exposed to ultraviolet light to cure the liquid crystalline monomer layer. In this way, the vertically aligned dichroic dye layer 6 can be obtained.

  Next, the operation of the viewing angle control display device of the present embodiment configured as described above will be described mainly with reference to FIG. From the backlight 5 and the vertically aligned dichroic dye layer 6, as shown in FIG. 4, polarized light having polarized light (A) 11 and polarized light (B) 12 is emitted. When the transparent / scattering switching element 7 is in a transparent state, these polarized lights are incident on the polarizing plate 8a. The polarized light (A) 11 that vibrates in parallel with the vertical transmission axis 9 of the polarizing plate 8a can pass through the polarizing plate 8a. On the other hand, the polarized light (B) 12 that vibrates perpendicularly to the transmission axis 9 of the polarizing plate 8a is absorbed by the polarizing plate 8a. For this reason, the distribution of light distribution incident on the display panel 10 is biased. In particular, oblique light in the plane Σ determined by the transmission axis 9 of the incident side polarizing plate 8a and the surface normal of the polarizing plate 8a is absorbed by the polarizing plate 8b. On the other hand, light incident from outside the Σ plane is not absorbed by the polarizing plate 8b. As described above, the vertically aligned dichroic dye layer 6 functions as a light beam regulating element that regulates the light beam direction.

  FIG. 8 is a cross-sectional view showing a layer structure when the viewing angle control display device of the first embodiment is embodied. A substrate on which a vertically oriented dichroic dye layer 6 is formed is mounted on the sidelight type backlight 5. Further, a transparent / scattering switching element 7 is mounted on the substrate on which the vertically aligned dichroic dye layer 6 is formed, and a polarizing plate 8a, a display panel 10 and a polarizing plate 8b are mounted thereon. . In the backlight 5, a prism sheet 18 is provided on the light guide plate 20, and a white LED (Light Emitting Diode) 19 is installed on the side of the light guide plate 20. The light emitted from the white LED 19 becomes planar light within the light guide plate 20, the directivity is enhanced by the prism sheet 18, and the light is emitted as a backlight light source. As the transparent / scattering switching element 7, a polymer dispersed liquid crystal (PDLC) in which a liquid crystal phase and a polymer phase are mixed can be used. The transparent / scattering switching element 7 includes a polymer-dispersed liquid crystal 23 disposed between a pair of plastic substrates 24. The polymer-dispersed liquid crystal 23 is obtained by dispersing liquid crystal droplets 22 in a resin 21. is there. As the display panel 10, a transmissive liquid crystal display panel or a transflective liquid crystal display panel can be used. FIG. 8 shows a transflective liquid crystal display panel. In the display panel 10, a reflective region 26 and a transmissive region 27 are provided on a substrate, and a color filter layer 28 is provided on a counter substrate, and a liquid crystal layer is provided between the substrate and the counter substrate. A substrate, a counter substrate, and a liquid crystal layer 25 are stacked with 25 interposed therebetween.

  The light from the backlight 5 becomes light that is collimated to some extent by the prism sheet 18. This collimated light is incident on the vertically aligned dichroic dye layer 6. As described above, in this vertically aligned dichroic dye layer 6, the oblique incident light is attenuated and emitted. The light emitted from the vertical alignment dichroic dye layer 6 enters the transparent / scattering switching element 7. The transparent / scattering switching element 7 can switch between a transparent state and a scattering state by switching between application and non-application of voltage. Thereby, the collimated light from the vertically aligned dichroic dye layer 6 is emitted as it is from the transparent / scattering switching element 7 as collimated light, or is changed into diffused light and emitted. Then, the collimated light or the diffused light enters the display panel 10 as transmitted light, and a display image is generated on the display panel 10. The polarizing plates 8a and 8b of the display panel 10 are arranged so that the transmission axis 9 is as shown in FIG. For this reason, in the case of collimated light, the light reaches only the observer positioned in front of the display panel 10, and the display light does not reach the observer positioned obliquely with respect to the display panel. For this reason, the display image is not recognized by an observer positioned in the diagonal direction of the display panel. On the other hand, in the case of diffused light, since the display light reaches the observer positioned in the diagonal direction of the display panel, the display image is also recognized by this observer.

  In this embodiment, the transparent / scattering switching element 7 has a structure in which a polymer dispersed liquid crystal 23 is sandwiched between a pair of plastic substrates 24. In order to put the above-mentioned display device into practical use, since there are many portable or portable applications, it is necessary to avoid an increase in the thickness of the display device. In particular, the current liquid crystal display device is designed to be extremely thin. Moreover, since the display apparatus of this embodiment has many portable or portable uses, it is desired that the mechanical durability is high. Therefore, it is preferable to manufacture these elements on the plastic substrate 24 described above.

  Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, a viewing angle control display having a laminated structure of a backlight 5 as a surface light source, a vertically aligned dichroic dye layer 6 as a light restricting element, a transparent / scattering switching element 7, and a display panel 10. In the apparatus, an optical compensation plate 13 as an optical compensation layer for correcting obliquely incident light into linearly polarized light is provided between the transparent / scattering switching element 7 and the polarizing plate 8a. A display panel and a polarizing plate (not shown) similar to the display panel 10 and the polarizing plate 8b shown in FIG. 4 are provided in front of the light transmission direction.

  As described above, PDLC or guest-host liquid crystal can be used for the transparent / scattering switching element 7. Usually, PDLC composed of liquid crystal molecules and a cured polymer resin is used. Therefore, there is a refractive index mismatch between the liquid crystal molecules and the polymer resin, and due to this refractive index mismatch, a scattering state is exhibited. In this PDLC, when a voltage is applied, the liquid crystals are aligned in the direction of the electric field, and the refractive indexes of the liquid crystal phase and the polymer phase match. For this reason, PDLC comes to exhibit a transparent state. In addition, since the liquid crystal is aligned perpendicular to the surface, the birefringence with respect to the front incident light disappears. However, it has birefringence for obliquely incident light. For this reason, when linearly polarized light is incident obliquely, elliptically polarized light is emitted. FIG. 5 illustrates this situation. In order to correct the elliptically polarized light, an optical compensation plate 13 is inserted between the transparent / scattering switching element 7 and the polarizing plate 8a. The optical compensator 13 corrects obliquely incident light to linearly polarized light. Therefore, when the light regulating element has the vertically aligned dichroic dye layer 6 including the dye 1 oriented in the normal direction of the substrate surface and the optical compensator 13, a more controlled light beam can be obtained. Become.

  FIG. 9 is a cross-sectional view showing a specific layer structure of the viewing angle control display device of the second embodiment. In the present embodiment, an optical compensation plate 13 is disposed between the vertically aligned dichroic dye layer 6 and the transparent / scattering switching element 7. In this case, as the optical compensator 13, for example, an optically negative uniaxial body having an optical axis in the surface normal direction can be used. When a voltage is applied to the transparent / scattering switching element 7, it changes to a transparent state, but at the same time, the liquid crystal molecules in the liquid crystal droplet 22 are aligned in the surface normal direction. For this reason, birefringence occurs with respect to light incident from an oblique direction. In order to compensate for this, an optically negative uniaxial body whose optical axis is in the surface normal direction is used as the optical compensator 13.

  FIG. 6 is a view showing a viewing angle control display device according to the third embodiment of the present invention. The third embodiment has a laminated structure of a backlight 5 as a surface light source, a display panel 10 such as a transmissive liquid crystal element, and a vertically aligned dichroic dye layer 6 as a light restricting element.

  Since the vertically oriented dichroic dye layer 6 has the optical characteristics shown in FIG. 3, the dichroic dye layer 6 is formed on the light emission side of the structure in which the backlight 5 as a surface light source and the display panel 10 are laminated. Even if it arrange | positions, diagonally incident light can be partially absorbed. However, this dichroic dye layer 6 does not absorb front incident light. For this reason, in the viewing angle control display device shown in FIG. 6, the viewing angle range cannot be made variable, but it absorbs the obliquely emitted light from the display panel without weakening the display light emitted to the front, The viewing angle range can be narrowed.

  FIG. 10 is a cross-sectional view showing a specific configuration of the viewing angle control display device of the third embodiment. In the display panel 10, for example, a transmission region 27 and a color filter layer 28 are formed on a pair of substrates provided so as to sandwich the liquid crystal layer 25, and polarizing plates 8 a and 8 b are respectively formed on the outside of the substrate. Is provided. The backlight 5 is provided with a white LED 19 on the side of the light guide plate 20, and light from the white LED 19 becomes a planar light source by the light guide plate 20 and enters the polarizing plate 8 a. A vertically aligned dichroic dye layer 6 is disposed above the marking panel 10.

  In this case, a part of the obliquely incident light from the display panel 10 to the vertical alignment dichroic dye layer 6 is absorbed by the vertical alignment dichroic dye layer 6. Therefore, the display light does not reach the observer positioned obliquely on the display device, and the display image cannot be recognized. As described above, the visibility angle range of the display image can be narrowed by using the configuration of FIG.

  The viewing angle control display device of each embodiment described above can be mounted on a telephone such as a mobile phone and a fixed phone, a mobile terminal, a PC (personal computer), a workstation, or the like.

It is a figure which shows the viewing angle control display apparatus of 1st Embodiment of this invention. It is a figure for demonstrating the function of a dichroic dye. It is a figure for demonstrating the function of a vertical alignment dichroic dye layer. It is a figure which similarly shows the operation | movement of 1st Embodiment of this invention. It is a figure which shows the viewing angle control display apparatus of 2nd Embodiment of this invention. It is a figure which shows the viewing angle control display apparatus of 3rd Embodiment of this invention. (A) thru | or (c) is a figure which shows the manufacturing method of a dichroic dye layer. It is sectional drawing about the specific layer structure of 1st Embodiment. It is sectional drawing about the specific layer structure of 2nd Embodiment. It is sectional drawing about the specific layer structure of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Dichroic dye 2 ... Unpolarized light 3 ... S polarized light 4 ... P polarized light 5 ... Back light 6 ... Vertically-aligned dichroic dye layer 7 ... Transparent Scattering switching elements 8a, 8b ... Polarizing plate 9 ... Transmission axis 10 ... Display panel 11 ... Polarized light (A)
12 ... Polarized light (B)
DESCRIPTION OF SYMBOLS 13 ... Optical compensator 14 ... Liquid crystalline monomer 15 ... Ultraviolet light 16 ... Orientation film 17 ... Substrate 18 ... Prism sheet 19 ... White LED
20 ... Light guide plate 21 ... Resin 22 ... Liquid crystal droplet 23 ... Polymer dispersed liquid crystal 24 ... Plastic substrate 25 ... Liquid crystal layer 26 ... Reflection area 27 ... Transmission area 28 ... Color filter layer

Claims (7)

A surface light source that emits light two-dimensionally, a light ray restricting element that restricts the direction of light rays from the surface light source, and a transparent light that switches between a transparent state and a scattering state with respect to the passage of light from the light ray restricting element. A scattering switching element; and a display panel for generating an image upon incidence of light from the surface light source, the light beam limiting element, or the transparent / scattering switching element, wherein the light beam limiting element is in a normal direction of the substrate surface A viewing angle control display device comprising an oriented dye layer. The viewing angle control display device according to claim 1, further comprising an optical compensation layer for correcting obliquely incident light into linearly polarized light. The said display panel is a liquid crystal display panel, The polarizing plate with which a transmission axis extends in the up-down direction of a display screen is arrange | positioned at the light incident side of this liquid crystal display panel. Viewing angle control display device. 4. The viewing angle control display device according to claim 1, wherein the display panel is disposed on a light emission side of the transparent / scattering switching element. 5. The viewing angle control display device according to any one of claims 1 to 3, wherein the display panel is disposed between the surface light source and the light beam restricting element. A terminal equipped with the viewing angle control display device according to any one of claims 1 to 5. The direction of the light from the surface light source is regulated by a light regulating element having a dye layer oriented in the normal direction of the substrate surface, and the transparent state and scattering are scattered by the transparent / scattering switching element with respect to the passage of light from the light regulating element. A viewing angle control display method characterized by switching a state and switching a visibility angle range of an image generated on a display panel.

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