US20100265438A1 - Double sided liquid crystal display unit and portable electronic apparatus comprising a polarizing element between two liquid crystal display panels - Google Patents
Double sided liquid crystal display unit and portable electronic apparatus comprising a polarizing element between two liquid crystal display panels Download PDFInfo
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- US20100265438A1 US20100265438A1 US12/828,476 US82847610A US2010265438A1 US 20100265438 A1 US20100265438 A1 US 20100265438A1 US 82847610 A US82847610 A US 82847610A US 2010265438 A1 US2010265438 A1 US 2010265438A1
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- liquid crystal
- crystal display
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- panel
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0033—Means for improving the coupling-out of light from the light guide
- G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0075—Arrangements of multiple light guides
- G02B6/0076—Stacked arrangements of multiple light guides of the same or different cross-sectional area
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/133342—Constructional arrangements; Manufacturing methods for double-sided displays
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/1336—Illuminating devices
- G02F1/133615—Edge-illuminating devices, i.e. illuminating from the side
Definitions
- the present invention relates to a liquid crystal display device, and specifically to a liquid crystal display device including two liquid crystal display panels located back to back.
- the present invention also relates to a mobile electronic device including such a liquid crystal display device.
- a two screen type mobile phone having a main display screen for displaying main information, and a sub display screen for displaying information in a supplementary manner where the phone is folded are popular owing to the convenience thereof.
- a two screen type mobile phone is described in, for example, Japanese Laid-Open Patent Publication No. 2001-136247.
- FIG. 16 shows a liquid crystal display device usable for two screen type mobile phones.
- a liquid crystal display device 800 shown in FIG. 16 includes two liquid crystal display panels 810 and 820 located back to back.
- One of the liquid crystal display panels, 810 is used for a main screen (hereinafter, referred to as a “main panel”), and the other liquid crystal display panel 820 is used for a sub screen (hereinafter, referred to as a “sub panel”).
- main panel main screen
- sub panel sub screen
- the main panel 810 includes a pair of substrates 810 a and 810 b , and a liquid crystal layer 812 provided therebetween.
- a pair of polarizing plates 801 and 802 are respectively provided outside the substrates 810 a and 810 b .
- the sub panel 820 includes a pair of substrates 820 a and 820 b , and a liquid crystal layer 822 provided therebetween.
- a pair of polarizing plates 803 and 804 are respectively provided outside the substrates 820 a and 820 b.
- the liquid crystal display device 800 also includes an illumination device 830 for emitting light toward the main panel 810 and an illumination device 840 for emitting light toward the sub panel 820 .
- the illumination device 830 for the main panel 810 is an edge light type backlight including a light source 831 and a light guide plate 832 for guiding the light emitted from the light source 831 toward the main panel 810 .
- the illumination device 840 for the sub panel 820 is also an edge light type backlight including a light source 841 and a light guide plate 842 for guiding the light emitted from the light source 841 toward the sub panel 820 .
- the liquid crystal display device 800 shown in FIG. 16 includes two liquid crystal display panels 810 and 820 and also two illumination devices, and therefore is about twice as thick as usual liquid crystal display devices including one liquid crystal display panel.
- preferred embodiments of the present invention reduce the thickness of a liquid crystal display device including two liquid crystal display panels located back to back.
- a liquid crystal display device includes a first liquid crystal display panel and a second liquid crystal display panel located back to back.
- the first liquid crystal display panel includes a first substrate, a second substrate located opposite from the second liquid crystal display panel with respect to the first substrate, a first liquid crystal layer provided between the first substrate and the second substrate, and a first polarizing element located opposite from the first substrate with respect to the first liquid crystal layer; and the second liquid crystal display panel includes a third substrate, a fourth substrate located opposite from the first liquid crystal display panel with respect to the third substrate, a second liquid crystal layer provided between the third substrate and the fourth substrate, and a second polarizing element located opposite from the third substrate with respect to the second liquid crystal layer.
- the liquid crystal display device further includes a first light source, provided to a side of the first substrate of the first liquid crystal display panel, for emitting light toward a side surface of the first substrate; a second light source, provided to a side of the third substrate of the second liquid crystal display panel, for emitting light toward a side surface of the third substrate; and a third polarizing element provided between the first liquid crystal display panel and the second liquid crystal display panel.
- the first substrate includes a first light guide layer for directing light, which is incident on the first substrate from the first light source and propagating inside the first substrate, toward the second liquid crystal display panel; and the third substrate includes a second light guide layer for directing light, which is incident on the third substrate from the second light source and propagating inside the third substrate, toward the first liquid crystal display panel.
- the first liquid crystal display panel performs display using light which has been output from the third substrate of the second liquid crystal display panel and passed through the third polarizing element; and the second liquid crystal display panel performs display using light which has been output from the first substrate of the first liquid crystal display panel and passed through the third polarizing element.
- the liquid crystal display device further includes a first dimmer provided between the first substrate and the third polarizing element, the first dimmer being switchable between a light reflective state and a light transmissive state; and a second dimmer provided between the third substrate and the third polarizing element, the second dimmer being switchable between the light reflective state and the light transmissive state.
- the first liquid crystal display panel performs display using light which has been output from the first substrate, passed through the first dimmer in the light transmissive state and the third polarizing element, and then reflected by the second dimmer in the light reflective state; and the second liquid crystal display panel performs display using light which has been output from the third substrate, passed through the second dimmer in the light transmissive state and the third polarizing element, and then reflected by the first dimmer in the light reflective state.
- the first dimmer and the second dimmer are each an electrochromic element, the light reflectance of which is changed in accordance with a voltage application.
- the first substrate includes a first transparent plate for supporting the first light guide layer, and a first low refractive index layer provided between the first transparent plate and the first liquid crystal layer and having a lower refractive index than that of the first transparent plate; and the third substrate includes a second transparent plate for supporting the second light guide layer, and a second low refractive index layer provided between the second transparent plate and the second liquid crystal layer and having a lower refractive index than that of the second transparent plate.
- the first light guide layer includes a plurality of first reflective films for reflecting the light, propagating inside the first substrate, toward the second liquid crystal display panel; and the second light guide layer includes a plurality of second reflective films for reflecting the light, propagating inside the third substrate, toward the first liquid crystal display panel.
- the plurality of first reflective films and the plurality of second reflective films are a plurality of dielectric films.
- a liquid crystal display device includes a first liquid crystal display panel and a second liquid crystal display panel located back to back.
- the first liquid crystal display panel includes a first substrate, a second substrate located opposite from the second liquid crystal display panel with respect to the first substrate, a first liquid crystal layer provided between the first substrate and the second substrate, and a first polarizing element located opposite from the first substrate with respect to the first liquid crystal layer; and the second liquid crystal display panel includes a third substrate, a fourth substrate located opposite from the first liquid crystal display panel with respect to the third substrate, a second liquid crystal layer provided between the third substrate and the fourth substrate, and a second polarizing element located opposite from the third substrate with respect to the second liquid crystal layer.
- the liquid crystal display device further includes a light source, provided to a side of the first substrate of the first liquid crystal display panel, for emitting light toward a side surface of the first substrate; a third polarizing element provided between the first liquid crystal display panel and the second liquid crystal display panel; and a dimmer provided between the third substrate and the third polarizing element, the dimmer being switchable between a light reflective state and a light transmissive state.
- the first substrate includes a light guide layer for directing light, which is incident on the first substrate from the first light source and propagating inside the first substrate, toward the second liquid crystal display panel.
- the first liquid crystal display panel performs display using light which has been output from the first substrate, passed through the third polarizing element, and then reflected by the dimmer in the light reflective state; and the second liquid crystal display panel performs display using light which has been output from the first substrate and passed through the third polarizing element and the dimmer in the light transmissive state.
- the dimmer is an electrochromic element, the light reflectance of which is changed in accordance with a voltage application.
- the first substrate includes a first transparent plate for supporting the first light guide layer, and a first low refractive index layer provided between the first transparent plate and the first liquid crystal layer and having a lower refractive index than that of the first transparent plate.
- the light guide layer includes a plurality of reflective films for reflecting the light, propagating inside the first substrate, toward the second liquid crystal display panel.
- the plurality of reflective films are a plurality of dielectric films.
- a mobile electronic device includes a liquid crystal display device having any of the above-described structures.
- the mobile electronic device according to the present invention is a foldable type mobile phone.
- the thickness of a liquid crystal display device including two liquid crystal display panels located back to back is greatly reduced.
- FIG. 1 is a cross-sectional view schematically showing a liquid crystal display device 100 according to a preferred embodiment of the present invention.
- FIG. 2 is a cross-sectional view showing a portion of the liquid crystal display device 100 .
- FIGS. 3A and 3B show exemplary shapes of reflective films of a light guide layer.
- FIGS. 4A and 4B show other exemplary shapes of the reflective films of the light guide layer.
- FIGS. 5A through 5D are cross-sectional views schematically showing steps of forming the light guide layer.
- FIGS. 6A through 6D are cross-sectional views schematically showing steps of forming the light guide layer.
- FIG. 7 is a cross-sectional view schematically showing another liquid crystal display device 200 according to a preferred embodiment of the present invention.
- FIGS. 8A and 8B show functions of a dimmer.
- FIG. 9 schematically shows how the first liquid crystal display panel of the liquid crystal display device 200 performs display.
- FIG. 10 schematically shows how the second liquid crystal display panel of the liquid crystal display device 200 performs display.
- FIG. 11 is a cross-sectional view schematically showing still another liquid crystal display device 300 according to a preferable embodiment of the present invention.
- FIG. 12 schematically shows how the first liquid crystal display panel of the liquid crystal display device 300 performs display.
- FIG. 13 schematically shows how the second liquid crystal display panel of the liquid crystal display device 300 performs display.
- FIGS. 14A and 14B show a folded state of a mobile phone 400 including a liquid crystal display device according to a preferred embodiment of the present invention; wherein FIG. 14A is a side view and FIG. 14B is a front view.
- FIGS. 15A , 15 B and 15 C show an opened state of the mobile phone 400 ; wherein FIG. 15A is a side view, FIG. 15B is a front view, and FIG. 15C is a rear view.
- FIG. 16 is a cross-sectional view schematically showing a conventional liquid crystal display device 800 used for a two screen type mobile phone.
- FIG. 1 shows a liquid crystal display device 100 according to this preferred embodiment.
- the liquid crystal display device 100 includes a first liquid crystal display panel 10 and a second liquid crystal display panel 20 located back to back.
- first liquid crystal display panel 10 will be referred to simply as a “first panel”
- second liquid crystal display panel 20 will be referred to simply as a “second panel”.
- the first panel 10 includes a pair of substrates 10 a and 10 b , and a liquid crystal layer 12 provided therebetween.
- the substrate 10 a which is closer to the second panel 20 will be referred to as a “rear substrate”
- the other substrate 10 b which is located opposite from the second panel 20 with respect to the rear substrate 10 a will be referred to as a “front substrate”.
- One of the rear substrate 10 a and the front substrate 10 b is, for example, an active matrix substrate, and the other is, for example, a color filter substrate.
- the active matrix substrate includes a switching element such as a TFT or the like and a pixel electrode
- the color filter substrate includes a color filter and a counter electrode.
- a polarizing plate (polarizing element) 1 is located at a position closer to an observer than the liquid crystal layer 12 , i.e., opposite from the rear substrate 10 a with respect to the liquid crystal layer 12 .
- the second panel 20 includes a pair of substrates 20 a and 20 b , and a liquid crystal layer 22 provided therebetween. Also regarding the second panel 20 , among the pair of substrates 20 a and 20 b , the substrate 20 a which is closer to the first panel will be referred to as a “rear substrate”, and the other substrate 20 b which is located opposite from the first panel 10 with respect to the rear substrate 20 a will be referred to as a “front substrate”.
- One of the rear substrate 20 a and the front substrate 20 b is, for example, an active matrix substrate, and the other is, for example, a color filter substrate.
- a polarizing plate (polarizing element) 2 is located at a position closer to the observer than the liquid crystal layer 22 , i.e., opposite from the rear substrate 20 a with respect to the liquid crystal layer 22 .
- the liquid crystal display device 100 also includes a first light source 11 provided to a side of the rear substrate 10 a of the first panel 10 , a second light source 21 provided to a side of the rear substrate 20 a of the second panel 20 , and a polarizing plate (polarizing element) 3 provided between the first panel 10 and the second panel 20 .
- the first light source 11 emits light toward a side surface of the rear substrate 10 a of the first panel 10
- the second light source 21 emits light toward a side surface of the rear substrate 20 a of the second panel 20 .
- An air layer 4 is present between the polarizing plate 3 and the first panel 10 , and between the polarizing plate 3 and the second panel 20 .
- the rear substrate 10 a of the first panel includes a light guide layer 14 for directing the light propagating inside the rear substrate 10 a toward the second panel 20 .
- the rear substrate 10 a also includes a transparent plate (e.g., a glass plate or a plastic plate) 13 for supporting the light guide layer 14 , and a low refractive index layer 15 provided between the transparent plate 13 and the liquid crystal layer 12 and having a lower refractive index than that of the transparent plate 13 .
- the low refractive index layer 15 is provided in order to totally reflect the light propagating inside the rear substrate 10 a efficiently at the interface between the transparent plate 13 and the low refractive index layer 15 .
- the rear substrate 20 a of the second panel 20 also includes a light guide layer 24 for directing the light propagating inside the rear substrate 20 a toward the first panel 10 .
- the rear substrate 20 a also includes a transparent plate (e.g., a glass plate or a plastic plate) 23 for supporting the light guide layer 24 , and a low refractive index layer 25 provided between the transparent plate 23 and the liquid crystal layer 22 and having a lower refractive index than that of the transparent plate 23 .
- the light propagating inside the rear substrate 10 a is output from the rear substrate 10 a toward the second panel 20 .
- the light output from the rear substrate 10 a passes through the polarizing plate 3 provided between the first panel 10 and the second panel 20 and is incident on the second panel 20 .
- the second panel 20 uses this light to perform display. Namely, the second panel 20 performs display using the light from the first light source 11 provided to the side of the rear substrate 10 a of the first panel 10 .
- the light propagating inside the rear substrate 20 a is output from the rear substrate 20 a toward the first panel 10 .
- the light output from the rear substrate 20 a passes through the polarizing plate 3 provided between the second panel 20 and the first panel 10 and is incident on the first panel 10 .
- the first panel 10 uses this light to perform display. Namely, the first panel 10 performs display using the light from the second light source 21 provided to the side of the rear substrate 20 a of the second panel 20 .
- the liquid crystal display device 100 in this preferred embodiment includes a light guide layer in the rear substrate of each of the two liquid crystal display panels, and allows light to be incident on the rear substrate from the light source provided to the side of the rear substrate.
- the rear substrate acts like a light guide plate. Therefore, as compared with the case where the backlight is used as shown in FIG. 16 , the entire thickness of the liquid crystal display device can be reduced by the thickness of the light guide plate, which is provided in the case of FIG. 16 but not in this preferred embodiment.
- each liquid crystal display panel directs the light toward the other liquid crystal display panel. Therefore, the light output from the rear substrate of each liquid crystal display panel passes through the polarizing plate located between the two liquid crystal display panels and then is incident on the other liquid crystal display panel to be used for display. Namely, in this preferred embodiment, one polarizing plate is shared by the two liquid crystal display panels, which can further reduce the thickness of the liquid crystal display device.
- the thickness of the liquid crystal display device including two liquid crystal display panels located back to back can be reduced as compared to the conventional art.
- the low refractive index layer 15 and 25 and the light guide layers 14 and 24 included in the rear substrates 10 a and 20 a will be described.
- the low refractive index layer 15 and the light guide layer 14 included in the rear substrate 10 a of the first panel 10 will be described as an example, but the following description is also applied to the low refractive index layer 25 and the light guide layer 24 included in the rear substrate 20 a of the second panel 20 .
- the low refractive index layer 15 may be formed of any material with no specific limitation as long as the material has a lower refractive index than that of the transparent plate 13 . In order to propagate light efficiently inside the rear substrate 10 a , however, the difference between the refractive index of the low refractive index layer 15 and the refractive index of the transparent plate 13 is preferably about 0.1 or greater, and more preferably about 0.18 or greater.
- the low refractive index layer 15 may be formed of, for example, MgF 2 (refractive index: about 1.38), a perfluoro resin (refractive index: about 1.34), or silicon oxide (refractive index: about 1.3).
- the light guide layer 14 in this preferred embodiment includes a plurality of reflective films 16 therein for reflecting the light propagating inside the rear substrate 10 a toward the second panel 20 .
- the reflective films 16 are inclined with respect to a main surface of the transparent plate 13 ; more specifically, are inclined such that an end thereof closer to the first light source 11 is closer to the transparent plate 13 than an end farther from the first light source 11 .
- the inclination angle of the reflective films 16 (the inclination angle with respect to the main surface of the transparent plate 13 ) is preferably about 50° or greater and about 60° or less, and more preferably about 51° for empirical reasons.
- the reflective films 16 may be metal films formed of aluminum, nickel, silver or the like, or may be dielectric films formed of SiO 2 , Al 2 O 3 or the like. Where dielectric films (which may be of a single layer or multiple layers) are used as the reflective films 16 , the luminance of the liquid crystal display device can be increased because specific linear polarization can be selectively reflected and thus the amount of light absorbed by the polarizing plate 3 can be reduced.
- a polarizing beam splitter which uses polarization dependence of the reflectance of a dielectric film and also uses light interference, can be designed such that the reflectance of S polarization is high while the reflectance of P polarization is kept low, by alternately stacking dielectric films having different refractive indexes with a thickness which fulfills the condition of ⁇ /4 with respect to a specific optical wavelength ⁇ (for example, “Kogaku Hakumaku” (Optical Thin Film), pp. 126-129, published by Kyoritsu Shuppan Co., Ltd.).
- the reflective films 16 of the light guide layer 14 can also be designed to have a low reflectance of P polarization and a high reflectance of S polarization, by forming dielectric films with a thickness which fulfills the condition of ⁇ /4.
- the reflective films 16 may have any shape (the shape as seen in the direction of the normal to the liquid crystal layer 12 ).
- the reflective films 16 may be formed as lines (strips) as shown in FIG. 3A and FIG. 4A , or in islands (dots) as shown in FIG. 3B and FIG. 4B .
- the reflective films 16 may be formed at a constant ratio as shown in FIGS. 3A and 3B , or may be formed so as to have a higher ratio as being farther from the first light source 11 as shown in FIGS. 4A and 4B .
- the amount of light propagating inside the rear substrate 10 a decreases the farther it is from the first light source 11 .
- the ratio of the reflective films 16 is increased the farther they are from the first light source 11 , the intensity distribution of the light which is output from the rear substrate 10 a can be uniform.
- the reflective films 16 may be formed at a constant repeating pitch while the area size thereof is increased as it is located farther from the first light source 11 .
- the reflective films 16 may be formed with substantially the same area size while the repeating pitch thereof is decreased the farther it is from the first light source 11 .
- a plurality of projections 18 having a right-angled triangular cross-section are formed of a resin (e.g., an ultraviolet curable resin having a refractive index of 1.53) on a flat plate-like film 17 formed of a resin (e.g., ZEONOR produced by Zeon Corporation having a refractive index of 1.53).
- a resin e.g., an ultraviolet curable resin having a refractive index of 1.53
- ZEONOR produced by Zeon Corporation having a refractive index of 1.53
- a dielectric material e.g., TiO 2 having a refractive index of 2.2 or ZrO 2 having a refractive index of 2.0
- the refractive films 16 are formed.
- an adhesive material e.g., an ultraviolet curable resin or a sticky material each having a refractive index of 1.53
- an adhesive layer 19 is formed.
- the adhesive layer 19 is put into contact with a surface of the transparent plate (e.g., a glass plate having a refractive index of 1.52) 13 and is cured.
- the light guide layer 14 is formed on the transparent plate 13 .
- a plurality of projections 18 having a right-angled triangular cross-section are formed of a resin on a flat plate-like film 17 formed of a resin.
- the projections 18 are formed with no gap, whereas in the step shown in FIG. 6A , the projections 18 are formed with prescribed gaps.
- the projections 18 are formed such that the gaps are narrower as being farther from the first light source 11 provided later.
- a dielectric material is vapor-deposited on the film 17 having the projections 18 formed thereon.
- the refractive films 16 are formed.
- the refractive films 16 are formed on inclined surfaces of the projections 18 and on portions of the film 17 on which the projection 18 is not formed.
- an adhesive material is applied so as to cover the reflective films 16 .
- an adhesive layer 19 is formed.
- the adhesive layer 19 is put into contact with a surface of the transparent plate 13 and is cured.
- the light guide layer 14 is formed on the transparent plate 13 .
- the reflective films 16 of the light guide layer 14 formed as shown in FIGS. 6A through 6D each have an inclined area 16 a which is inclined with respect to the main surface of the transparent plate 13 and a parallel area 16 b which is parallel to the main surface.
- the inclined area 16 a contributes to outputting light and substantially acts as a reflective film.
- the steps shown in FIGS. 5A through 5D require the locations of the reflective films 16 to be controlled by use of the mask 30 .
- the steps shown in FIGS. 6A through 6D can control the locations of the inclined areas 16 a , substantially acting as the reflective films, merely by appropriately setting the locations of the projections 18 . This simplifies the formation steps.
- a liquid crystal display device 200 according to this preferred embodiment will be described. In the following, differences of the liquid crystal display device 200 from the liquid crystal display device 100 in Preferred Embodiment 1 will be mainly described.
- the liquid crystal display device 200 includes a first dimmer 31 provided between the rear substrate 10 a of the first panel 10 and the polarizing plate 3 , and a second dimmer 32 provided between the rear substrate 20 a of the second panel 20 and the polarizing plate 3 .
- the first dimmer 31 and the second dimmer 32 can both be switched between a light reflective state and a light transmissive state.
- the first dimmer 31 is provided on the rear substrate 10 a of the first panel 10
- the second dimmer 32 is provided on the rear substrate 20 a of the second panel 20 .
- the polarizing plate 3 is bonded to the first dimmer 31
- the second dimmer 32 and the polarizing plate 3 are bonded together with a gel-like transparent sticky material 34 .
- the liquid crystal display device 200 including the first dimmer 31 and the second dimmer 32 performs display as follows.
- the first dimmer 31 is in the light transmissive state and the second dimmer 32 is in the light reflective state. Namely, the first panel 10 performs display using light which has been output from the rear substrate 10 a of the first panel 10 , passed through the first dimmer 31 in the light transmissive state and the polarizing plate 3 , and then reflected by the second dimmer 32 in the light reflective state.
- the first dimmer 31 is in the light reflective state and the second dimmer 32 is in the light transmissive state.
- the second panel 20 performs display using light which has been output from the rear substrate 20 a of the second panel 20 , passed through the second dimmer 32 in the light transmissive state and the polarizing plate 3 , and then reflected by the first dimmer 31 in the light reflective state.
- the rear substrate of each of the two liquid crystal display panels acts as a light guide plate. Therefore, as compared with the case where the backlight is used as shown in FIG. 16 , the entire thickness of the liquid crystal display device can be reduced by the thickness of the light guide plate, which is provided in the case of FIG. 16 but not in this embodiment.
- one polarizing plate 3 is shared by the two liquid crystal display panels, which can further reduce the thickness of the liquid crystal display device.
- first dimmer 31 and the second dimmer are switched between the light transmissive state and the light reflective state in synchronization with the driving of the first panel 10 and the second panel 20 . This allows the two panels to appear as being lit up at the same time.
- An electrochromic element includes a dimmer layer formed of a material, the light reflectance of which is reversibly changed by electrochemical oxidation and reduction reactions, and a pair of transparent conductive layers for applying a voltage to the dimmer layer.
- the dimmer layer is, for example, a rare earth metal thin film of yttrium, lanthanum or the like, or a magnesium-nickel alloy thin film covered with palladium or the like.
- An electrochromic element in the light reflective state specular-reflects light. For this reason, in order to prevent external light from being imaged or in order to enlarge the viewing angle, it is preferable to provide a light scattering element.
- polarizing plates with a light scattering layer may be preferably used as the polarizing plates 1 and 2 .
- elements other than the electrochromic element may be used.
- a gaschromic element is usable. The light reflectance of a gaschromic element is reversibly changed in accordance with the concentration of a specific chemical element in the atmosphere.
- a usable material for the gaschromic element may be, for example, a magnesium-nickel alloy thin film.
- a liquid crystal display device 300 according to this preferred embodiment will be described. In the following, differences of the liquid crystal display device 300 from the liquid crystal display device 200 in Preferred Embodiment 2 will be mainly described.
- the light source 11 is provided to a side of the rear substrate 10 a of the first panel 10 , but no light source is provided to a side of the rear substrate 20 a of the second panel 20 .
- the dimmer 32 is provided between the rear substrate 20 a of the second panel 20 and the polarizing plate 3 , but no dimmer is provided between the rear substrate 10 a of the first panel 10 and the polarizing plate 3 .
- the rear substrate 10 a of the first panel 10 includes the light guide layer 14 and the low refractive index layer 15
- the rear substrate 20 a of the second panel 20 includes neither the light guide layer nor the low refractive index layer.
- the liquid crystal display device 300 in this preferred embodiment performs display as follows.
- the first dimmer 32 is in the light reflective state. Namely, the first panel 10 performs display using light which has been output from the rear substrate 10 a of the first panel 10 , passed through the polarizing plate 3 , and then reflected by the dimmer 32 in the light reflective state.
- the dimmer 32 is in the light transmissive state. Namely, the second panel 20 performs display using light which has been output from the rear substrate 10 a of the first panel 10 and passed through the polarizing plate 3 and the dimmer 32 in the light transmissive state.
- the entire thickness of the liquid crystal display device can be reduced by the thickness of the light guide plate, which is provided in the case of FIG. 16 but not in this embodiment.
- one polarizing plate 3 is shared by the two liquid crystal display panels, which can further reduce the thickness of the liquid crystal display device.
- the light source does not need to be provided to the side of the rear substrate 20 a of the second panel 20 , which can reduce the production cost.
- the rear substrate 20 a of the second panel 20 does not need to include a light guide layer or a low refractive index layer, which can further reduce the production cost.
- FIGS. 11 through 13 show the first panel 10 and the second panel 20 with substantially the same size (i.e., the display screens are shown with substantially the same size).
- the second panel 20 may be smaller than (i.e., may have a smaller display screen than that of) the first panel 10 because the rear substrate 20 a of the second panel 20 does not need to include a light guide layer.
- the second panel 20 has a higher degree of designing freedom.
- the dimmer 32 is switched between the light transmissive state and the light reflective state in synchronization with the driving of the first panel 10 and the second panel 20 . This allows the two panels to appear as being lit up at the same time.
- FIGS. 14A and 14 B and FIGS. 15A-15D show a foldable type phone 400 including a liquid crystal display device according to the present invention.
- FIGS. 14A and 14B show a folded state, wherein FIG. 14A is a side view and FIG. 14B is a front view.
- FIGS. 15A , 15 B and 15 C show an opened state, wherein FIG. 15A is a side view, FIG. 15B is a front view, and FIG. 15C is a rear view.
- the mobile phone 400 is a so-called two screen type mobile phone including a main display screen 60 A for displaying main information and a sub display screen 60 B for displaying supplementary information.
- the sub display screen 60 B displays, for example, the radio wave receiving state, the remaining battery life or the like.
- the mobile phone 400 includes a liquid crystal display device according to any of the various preferred embodiments of the present invention (in the figures, the elements other than the first panel 10 and the second panel 20 are omitted) and a housing for accommodating various elements including the liquid crystal display device.
- the housing includes a display section 60 for accommodating the liquid crystal display device, an operation section 70 including operation keys 71 , and a connection section (e.g., a hinge) 80 for connecting the display section 60 and the operation section 70 .
- the housing is foldable at the connection section 80 .
- the mobile phone 400 includes a liquid crystal display device according to any of the various preferred embodiments of the present invention in the display section 60 , and therefore can have a reduced thickness than the conventional mobile phones.
- a liquid crystal display device can have a reduced thickness than the conventional mobile phones, and is preferably usable for various types of mobile electronic devices, especially preferably for foldable type mobile phones.
Abstract
Description
- 1. Field of the Invention
- The present invention relates to a liquid crystal display device, and specifically to a liquid crystal display device including two liquid crystal display panels located back to back. The present invention also relates to a mobile electronic device including such a liquid crystal display device.
- 2. Description of the Related Art
- Recently, mobile phones have been progressively spread, and foldable type phones are now mainstream. Especially, two screen type phones having a main display screen for displaying main information, and a sub display screen for displaying information in a supplementary manner where the phone is folded are popular owing to the convenience thereof. A two screen type mobile phone is described in, for example, Japanese Laid-Open Patent Publication No. 2001-136247.
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FIG. 16 shows a liquid crystal display device usable for two screen type mobile phones. A liquidcrystal display device 800 shown inFIG. 16 includes two liquidcrystal display panels crystal display panel 820 is used for a sub screen (hereinafter, referred to as a “sub panel”). - The
main panel 810 includes a pair ofsubstrates liquid crystal layer 812 provided therebetween. A pair of polarizingplates substrates sub panel 820 includes a pair ofsubstrates liquid crystal layer 822 provided therebetween. A pair of polarizingplates substrates - The liquid
crystal display device 800 also includes anillumination device 830 for emitting light toward themain panel 810 and anillumination device 840 for emitting light toward thesub panel 820. Theillumination device 830 for themain panel 810 is an edge light type backlight including alight source 831 and alight guide plate 832 for guiding the light emitted from thelight source 831 toward themain panel 810. Theillumination device 840 for thesub panel 820 is also an edge light type backlight including alight source 841 and alight guide plate 842 for guiding the light emitted from thelight source 841 toward thesub panel 820. - Today, mobile phones are desired to be thinner so that the user is not disturbed by the thickness thereof even in a folded state, and thus the liquid crystal display devices used for the mobile phones are also desired to be thinner.
- However, the liquid
crystal display device 800 shown inFIG. 16 includes two liquidcrystal display panels - In order to overcome the problems described above, preferred embodiments of the present invention reduce the thickness of a liquid crystal display device including two liquid crystal display panels located back to back.
- A liquid crystal display device according to a preferred embodiment of the present invention includes a first liquid crystal display panel and a second liquid crystal display panel located back to back. The first liquid crystal display panel includes a first substrate, a second substrate located opposite from the second liquid crystal display panel with respect to the first substrate, a first liquid crystal layer provided between the first substrate and the second substrate, and a first polarizing element located opposite from the first substrate with respect to the first liquid crystal layer; and the second liquid crystal display panel includes a third substrate, a fourth substrate located opposite from the first liquid crystal display panel with respect to the third substrate, a second liquid crystal layer provided between the third substrate and the fourth substrate, and a second polarizing element located opposite from the third substrate with respect to the second liquid crystal layer. The liquid crystal display device further includes a first light source, provided to a side of the first substrate of the first liquid crystal display panel, for emitting light toward a side surface of the first substrate; a second light source, provided to a side of the third substrate of the second liquid crystal display panel, for emitting light toward a side surface of the third substrate; and a third polarizing element provided between the first liquid crystal display panel and the second liquid crystal display panel. The first substrate includes a first light guide layer for directing light, which is incident on the first substrate from the first light source and propagating inside the first substrate, toward the second liquid crystal display panel; and the third substrate includes a second light guide layer for directing light, which is incident on the third substrate from the second light source and propagating inside the third substrate, toward the first liquid crystal display panel. The above-described advantages are achieved by this structure.
- In a preferred embodiment of the present invention, the first liquid crystal display panel performs display using light which has been output from the third substrate of the second liquid crystal display panel and passed through the third polarizing element; and the second liquid crystal display panel performs display using light which has been output from the first substrate of the first liquid crystal display panel and passed through the third polarizing element.
- In a preferred embodiment of the present invention, the liquid crystal display device according to a preferred embodiment of the present invention further includes a first dimmer provided between the first substrate and the third polarizing element, the first dimmer being switchable between a light reflective state and a light transmissive state; and a second dimmer provided between the third substrate and the third polarizing element, the second dimmer being switchable between the light reflective state and the light transmissive state.
- In a preferred embodiment of the present invention, the first liquid crystal display panel performs display using light which has been output from the first substrate, passed through the first dimmer in the light transmissive state and the third polarizing element, and then reflected by the second dimmer in the light reflective state; and the second liquid crystal display panel performs display using light which has been output from the third substrate, passed through the second dimmer in the light transmissive state and the third polarizing element, and then reflected by the first dimmer in the light reflective state.
- In a preferred embodiment of the present invention, the first dimmer and the second dimmer are each an electrochromic element, the light reflectance of which is changed in accordance with a voltage application.
- In a preferred embodiment of the present invention, the first substrate includes a first transparent plate for supporting the first light guide layer, and a first low refractive index layer provided between the first transparent plate and the first liquid crystal layer and having a lower refractive index than that of the first transparent plate; and the third substrate includes a second transparent plate for supporting the second light guide layer, and a second low refractive index layer provided between the second transparent plate and the second liquid crystal layer and having a lower refractive index than that of the second transparent plate.
- In a preferred embodiment of the present invention, the first light guide layer includes a plurality of first reflective films for reflecting the light, propagating inside the first substrate, toward the second liquid crystal display panel; and the second light guide layer includes a plurality of second reflective films for reflecting the light, propagating inside the third substrate, toward the first liquid crystal display panel.
- In a preferred embodiment of the present invention, the plurality of first reflective films and the plurality of second reflective films are a plurality of dielectric films.
- Alternatively, a liquid crystal display device according to a preferred embodiment the present invention includes a first liquid crystal display panel and a second liquid crystal display panel located back to back. The first liquid crystal display panel includes a first substrate, a second substrate located opposite from the second liquid crystal display panel with respect to the first substrate, a first liquid crystal layer provided between the first substrate and the second substrate, and a first polarizing element located opposite from the first substrate with respect to the first liquid crystal layer; and the second liquid crystal display panel includes a third substrate, a fourth substrate located opposite from the first liquid crystal display panel with respect to the third substrate, a second liquid crystal layer provided between the third substrate and the fourth substrate, and a second polarizing element located opposite from the third substrate with respect to the second liquid crystal layer. The liquid crystal display device further includes a light source, provided to a side of the first substrate of the first liquid crystal display panel, for emitting light toward a side surface of the first substrate; a third polarizing element provided between the first liquid crystal display panel and the second liquid crystal display panel; and a dimmer provided between the third substrate and the third polarizing element, the dimmer being switchable between a light reflective state and a light transmissive state. The first substrate includes a light guide layer for directing light, which is incident on the first substrate from the first light source and propagating inside the first substrate, toward the second liquid crystal display panel. The above-described advantages are achieved by this structure.
- In a preferred embodiment of the present invention, the first liquid crystal display panel performs display using light which has been output from the first substrate, passed through the third polarizing element, and then reflected by the dimmer in the light reflective state; and the second liquid crystal display panel performs display using light which has been output from the first substrate and passed through the third polarizing element and the dimmer in the light transmissive state.
- In a preferred embodiment of the present invention, the dimmer is an electrochromic element, the light reflectance of which is changed in accordance with a voltage application.
- In a preferred embodiment of the present invention, the first substrate includes a first transparent plate for supporting the first light guide layer, and a first low refractive index layer provided between the first transparent plate and the first liquid crystal layer and having a lower refractive index than that of the first transparent plate.
- In a preferred embodiment of the present invention, the light guide layer includes a plurality of reflective films for reflecting the light, propagating inside the first substrate, toward the second liquid crystal display panel.
- In a preferred embodiment of the present invention, the plurality of reflective films are a plurality of dielectric films.
- A mobile electronic device according to another preferred embodiment of the present invention includes a liquid crystal display device having any of the above-described structures.
- In a preferred embodiment of the present invention, the mobile electronic device according to the present invention is a foldable type mobile phone.
- According to various preferred embodiments of the present invention, the thickness of a liquid crystal display device including two liquid crystal display panels located back to back is greatly reduced.
- Other features, elements, processes, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.
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FIG. 1 is a cross-sectional view schematically showing a liquidcrystal display device 100 according to a preferred embodiment of the present invention. -
FIG. 2 is a cross-sectional view showing a portion of the liquidcrystal display device 100. -
FIGS. 3A and 3B show exemplary shapes of reflective films of a light guide layer. -
FIGS. 4A and 4B show other exemplary shapes of the reflective films of the light guide layer. -
FIGS. 5A through 5D are cross-sectional views schematically showing steps of forming the light guide layer. -
FIGS. 6A through 6D are cross-sectional views schematically showing steps of forming the light guide layer. -
FIG. 7 is a cross-sectional view schematically showing another liquidcrystal display device 200 according to a preferred embodiment of the present invention. -
FIGS. 8A and 8B show functions of a dimmer. -
FIG. 9 schematically shows how the first liquid crystal display panel of the liquidcrystal display device 200 performs display. -
FIG. 10 schematically shows how the second liquid crystal display panel of the liquidcrystal display device 200 performs display. -
FIG. 11 is a cross-sectional view schematically showing still another liquidcrystal display device 300 according to a preferable embodiment of the present invention. -
FIG. 12 schematically shows how the first liquid crystal display panel of the liquidcrystal display device 300 performs display. -
FIG. 13 schematically shows how the second liquid crystal display panel of the liquidcrystal display device 300 performs display. -
FIGS. 14A and 14B show a folded state of amobile phone 400 including a liquid crystal display device according to a preferred embodiment of the present invention; whereinFIG. 14A is a side view andFIG. 14B is a front view. -
FIGS. 15A , 15B and 15C show an opened state of themobile phone 400; whereinFIG. 15A is a side view,FIG. 15B is a front view, andFIG. 15C is a rear view. -
FIG. 16 is a cross-sectional view schematically showing a conventional liquidcrystal display device 800 used for a two screen type mobile phone. - Hereinafter, the present invention will be described by way of preferred embodiments with reference to the drawings. The present invention is not limited to the following preferred embodiments.
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FIG. 1 shows a liquidcrystal display device 100 according to this preferred embodiment. As shown inFIG. 1 , the liquidcrystal display device 100 includes a first liquidcrystal display panel 10 and a second liquidcrystal display panel 20 located back to back. Hereinafter, the first liquidcrystal display panel 10 will be referred to simply as a “first panel”, and the second liquidcrystal display panel 20 will be referred to simply as a “second panel”. - The
first panel 10 includes a pair ofsubstrates liquid crystal layer 12 provided therebetween. Among the pair ofsubstrates substrate 10 a which is closer to thesecond panel 20 will be referred to as a “rear substrate”, and theother substrate 10 b which is located opposite from thesecond panel 20 with respect to therear substrate 10 a will be referred to as a “front substrate”. One of therear substrate 10 a and thefront substrate 10 b is, for example, an active matrix substrate, and the other is, for example, a color filter substrate. Although not shown here, the active matrix substrate includes a switching element such as a TFT or the like and a pixel electrode, and the color filter substrate includes a color filter and a counter electrode. A polarizing plate (polarizing element) 1 is located at a position closer to an observer than theliquid crystal layer 12, i.e., opposite from therear substrate 10 a with respect to theliquid crystal layer 12. - The
second panel 20 includes a pair ofsubstrates liquid crystal layer 22 provided therebetween. Also regarding thesecond panel 20, among the pair ofsubstrates substrate 20 a which is closer to the first panel will be referred to as a “rear substrate”, and theother substrate 20 b which is located opposite from thefirst panel 10 with respect to therear substrate 20 a will be referred to as a “front substrate”. One of therear substrate 20 a and thefront substrate 20 b is, for example, an active matrix substrate, and the other is, for example, a color filter substrate. A polarizing plate (polarizing element) 2 is located at a position closer to the observer than theliquid crystal layer 22, i.e., opposite from therear substrate 20 a with respect to theliquid crystal layer 22. - The liquid
crystal display device 100 also includes afirst light source 11 provided to a side of therear substrate 10 a of thefirst panel 10, a secondlight source 21 provided to a side of therear substrate 20 a of thesecond panel 20, and a polarizing plate (polarizing element) 3 provided between thefirst panel 10 and thesecond panel 20. Thefirst light source 11 emits light toward a side surface of therear substrate 10 a of thefirst panel 10, and the secondlight source 21 emits light toward a side surface of therear substrate 20 a of thesecond panel 20. Anair layer 4 is present between thepolarizing plate 3 and thefirst panel 10, and between thepolarizing plate 3 and thesecond panel 20. - Light emitted from the
first light source 11 is incident on therear substrate 10 a of thefirst panel 10 and is propagating inside therear substrate 10 a while being totally reflected repeatedly. Therear substrate 10 a of the first panel includes alight guide layer 14 for directing the light propagating inside therear substrate 10 a toward thesecond panel 20. Therear substrate 10 a also includes a transparent plate (e.g., a glass plate or a plastic plate) 13 for supporting thelight guide layer 14, and a lowrefractive index layer 15 provided between thetransparent plate 13 and theliquid crystal layer 12 and having a lower refractive index than that of thetransparent plate 13. The lowrefractive index layer 15 is provided in order to totally reflect the light propagating inside therear substrate 10 a efficiently at the interface between thetransparent plate 13 and the lowrefractive index layer 15. - Light emitted from the second
light source 21 is incident on therear substrate 20 a of thesecond panel 20 and propagates inside therear substrate 20 a while being totally reflected repeatedly. Therear substrate 20 a of thesecond panel 20 also includes alight guide layer 24 for directing the light propagating inside therear substrate 20 a toward thefirst panel 10. Therear substrate 20 a also includes a transparent plate (e.g., a glass plate or a plastic plate) 23 for supporting thelight guide layer 24, and a lowrefractive index layer 25 provided between thetransparent plate 23 and theliquid crystal layer 22 and having a lower refractive index than that of thetransparent plate 23. - Owing to the
light guide layer 14 provided in therear substrate 10 a of thefirst panel 10, the light propagating inside therear substrate 10 a is output from therear substrate 10 a toward thesecond panel 20. The light output from therear substrate 10 a passes through thepolarizing plate 3 provided between thefirst panel 10 and thesecond panel 20 and is incident on thesecond panel 20. Thesecond panel 20 uses this light to perform display. Namely, thesecond panel 20 performs display using the light from thefirst light source 11 provided to the side of therear substrate 10 a of thefirst panel 10. - Owing to the
light guide layer 24 provided in therear substrate 20 a of thefirst panel 20, the light propagating inside therear substrate 20 a is output from therear substrate 20 a toward thefirst panel 10. The light output from therear substrate 20 a passes through thepolarizing plate 3 provided between thesecond panel 20 and thefirst panel 10 and is incident on thefirst panel 10. Thefirst panel 10 uses this light to perform display. Namely, thefirst panel 10 performs display using the light from the secondlight source 21 provided to the side of therear substrate 20 a of thesecond panel 20. - As described above, the liquid
crystal display device 100 in this preferred embodiment includes a light guide layer in the rear substrate of each of the two liquid crystal display panels, and allows light to be incident on the rear substrate from the light source provided to the side of the rear substrate. Thus, the rear substrate acts like a light guide plate. Therefore, as compared with the case where the backlight is used as shown inFIG. 16 , the entire thickness of the liquid crystal display device can be reduced by the thickness of the light guide plate, which is provided in the case ofFIG. 16 but not in this preferred embodiment. - In addition, the light guide layer of each liquid crystal display panel directs the light toward the other liquid crystal display panel. Therefore, the light output from the rear substrate of each liquid crystal display panel passes through the polarizing plate located between the two liquid crystal display panels and then is incident on the other liquid crystal display panel to be used for display. Namely, in this preferred embodiment, one polarizing plate is shared by the two liquid crystal display panels, which can further reduce the thickness of the liquid crystal display device.
- As described above, according to preferred embodiments of the present invention, the thickness of the liquid crystal display device including two liquid crystal display panels located back to back can be reduced as compared to the conventional art.
- Now, specific structures of the low refractive index layers 15 and 25 and the light guide layers 14 and 24 included in the
rear substrates refractive index layer 15 and thelight guide layer 14 included in therear substrate 10 a of thefirst panel 10 will be described as an example, but the following description is also applied to the lowrefractive index layer 25 and thelight guide layer 24 included in therear substrate 20 a of thesecond panel 20. - The low
refractive index layer 15 may be formed of any material with no specific limitation as long as the material has a lower refractive index than that of thetransparent plate 13. In order to propagate light efficiently inside therear substrate 10 a, however, the difference between the refractive index of the lowrefractive index layer 15 and the refractive index of thetransparent plate 13 is preferably about 0.1 or greater, and more preferably about 0.18 or greater. The lowrefractive index layer 15 may be formed of, for example, MgF2 (refractive index: about 1.38), a perfluoro resin (refractive index: about 1.34), or silicon oxide (refractive index: about 1.3). - As shown in
FIG. 2 , thelight guide layer 14 in this preferred embodiment includes a plurality ofreflective films 16 therein for reflecting the light propagating inside therear substrate 10 a toward thesecond panel 20. Thereflective films 16 are inclined with respect to a main surface of thetransparent plate 13; more specifically, are inclined such that an end thereof closer to thefirst light source 11 is closer to thetransparent plate 13 than an end farther from thefirst light source 11. The inclination angle of the reflective films 16 (the inclination angle with respect to the main surface of the transparent plate 13) is preferably about 50° or greater and about 60° or less, and more preferably about 51° for empirical reasons. - The
reflective films 16 may be metal films formed of aluminum, nickel, silver or the like, or may be dielectric films formed of SiO2, Al2O3 or the like. Where dielectric films (which may be of a single layer or multiple layers) are used as thereflective films 16, the luminance of the liquid crystal display device can be increased because specific linear polarization can be selectively reflected and thus the amount of light absorbed by thepolarizing plate 3 can be reduced. - Now, a preferable thickness of the
reflective films 16 formed of dielectric films will be described. It is known that a polarizing beam splitter, which uses polarization dependence of the reflectance of a dielectric film and also uses light interference, can be designed such that the reflectance of S polarization is high while the reflectance of P polarization is kept low, by alternately stacking dielectric films having different refractive indexes with a thickness which fulfills the condition of λ/4 with respect to a specific optical wavelength λ (for example, “Kogaku Hakumaku” (Optical Thin Film), pp. 126-129, published by Kyoritsu Shuppan Co., Ltd.). There are various known dielectric materials including MgF2, SiO2, Al2O3, TiO2 and ZrO2 (for example, “Oyobutsurikogaku Sensho 3, Hakumaku” (Applied Physical Engineering, selectedbook 3, Thin Film) page 203 published by Baifukan Kabushiki Kaisha). Thereflective films 16 of thelight guide layer 14 can also be designed to have a low reflectance of P polarization and a high reflectance of S polarization, by forming dielectric films with a thickness which fulfills the condition of λ/4. - The
reflective films 16 may have any shape (the shape as seen in the direction of the normal to the liquid crystal layer 12). Thereflective films 16 may be formed as lines (strips) as shown inFIG. 3A andFIG. 4A , or in islands (dots) as shown inFIG. 3B andFIG. 4B . - The
reflective films 16 may be formed at a constant ratio as shown inFIGS. 3A and 3B , or may be formed so as to have a higher ratio as being farther from thefirst light source 11 as shown inFIGS. 4A and 4B . The amount of light propagating inside therear substrate 10 a decreases the farther it is from thefirst light source 11. Where the ratio of thereflective films 16 is increased the farther they are from thefirst light source 11, the intensity distribution of the light which is output from therear substrate 10 a can be uniform. As shown inFIGS. 4A and 4B , thereflective films 16 may be formed at a constant repeating pitch while the area size thereof is increased as it is located farther from thefirst light source 11. Alternatively, thereflective films 16 may be formed with substantially the same area size while the repeating pitch thereof is decreased the farther it is from thefirst light source 11. - Now, with reference to
FIGS. 5A through 5D , one exemplary method for forming thelight guide layer 14 will be described. - First, as shown in
FIG. 5A , a plurality ofprojections 18 having a right-angled triangular cross-section are formed of a resin (e.g., an ultraviolet curable resin having a refractive index of 1.53) on a flat plate-like film 17 formed of a resin (e.g., ZEONOR produced by Zeon Corporation having a refractive index of 1.53). - Next, as shown in
FIG. 5B , on inclined surfaces of the projections 18 (the surfaces inclined with respect to a main surface of the film 17), a dielectric material (e.g., TiO2 having a refractive index of 2.2 or ZrO2 having a refractive index of 2.0) is vapor-deposited via amask 30. Thus, therefractive films 16 are formed. - Next, as shown in
FIG. 5C , an adhesive material (e.g., an ultraviolet curable resin or a sticky material each having a refractive index of 1.53) is applied so as to cover theprojections 18. Thus, anadhesive layer 19 is formed. - Then, as shown in
FIG. 5D , theadhesive layer 19 is put into contact with a surface of the transparent plate (e.g., a glass plate having a refractive index of 1.52) 13 and is cured. Thus, thelight guide layer 14 is formed on thetransparent plate 13. - Now, with reference to
FIGS. 6A through 6D , another exemplary method for forming thelight guide layer 14 will be described. - First, as shown in
FIG. 6A , a plurality ofprojections 18 having a right-angled triangular cross-section are formed of a resin on a flat plate-like film 17 formed of a resin. In the step shown inFIG. 5A , theprojections 18 are formed with no gap, whereas in the step shown inFIG. 6A , theprojections 18 are formed with prescribed gaps. Theprojections 18 are formed such that the gaps are narrower as being farther from thefirst light source 11 provided later. - Next, as shown in
FIG. 6B , a dielectric material is vapor-deposited on thefilm 17 having theprojections 18 formed thereon. Thus, therefractive films 16 are formed. By this step, therefractive films 16 are formed on inclined surfaces of theprojections 18 and on portions of thefilm 17 on which theprojection 18 is not formed. - Next, as shown in
FIG. 6C , an adhesive material is applied so as to cover thereflective films 16. Thus, anadhesive layer 19 is formed. - Then, as shown in
FIG. 6D , theadhesive layer 19 is put into contact with a surface of thetransparent plate 13 and is cured. Thus, thelight guide layer 14 is formed on thetransparent plate 13. - The
reflective films 16 of thelight guide layer 14 formed as shown inFIGS. 6A through 6D each have an inclinedarea 16 a which is inclined with respect to the main surface of thetransparent plate 13 and aparallel area 16 b which is parallel to the main surface. Theinclined area 16 a contributes to outputting light and substantially acts as a reflective film. - The steps shown in
FIGS. 5A through 5D require the locations of thereflective films 16 to be controlled by use of themask 30. By contrast, the steps shown inFIGS. 6A through 6D can control the locations of theinclined areas 16 a, substantially acting as the reflective films, merely by appropriately setting the locations of theprojections 18. This simplifies the formation steps. - With reference to
FIG. 7 , a liquidcrystal display device 200 according to this preferred embodiment will be described. In the following, differences of the liquidcrystal display device 200 from the liquidcrystal display device 100 inPreferred Embodiment 1 will be mainly described. - As shown in
FIG. 7 , unlike the liquidcrystal display device 100 inPreferred Embodiment 1, the liquidcrystal display device 200 includes afirst dimmer 31 provided between therear substrate 10 a of thefirst panel 10 and thepolarizing plate 3, and asecond dimmer 32 provided between therear substrate 20 a of thesecond panel 20 and thepolarizing plate 3. - As schematically shown in
FIGS. 8A and 8B , thefirst dimmer 31 and thesecond dimmer 32 can both be switched between a light reflective state and a light transmissive state. In this preferred embodiment, thefirst dimmer 31 is provided on therear substrate 10 a of thefirst panel 10, and thesecond dimmer 32 is provided on therear substrate 20 a of thesecond panel 20. Thepolarizing plate 3 is bonded to thefirst dimmer 31, and thesecond dimmer 32 and thepolarizing plate 3 are bonded together with a gel-like transparentsticky material 34. - The liquid
crystal display device 200 including thefirst dimmer 31 and thesecond dimmer 32 performs display as follows. - When the
first panel 10 is to perform display, as shown inFIG. 9 , thefirst dimmer 31 is in the light transmissive state and thesecond dimmer 32 is in the light reflective state. Namely, thefirst panel 10 performs display using light which has been output from therear substrate 10 a of thefirst panel 10, passed through thefirst dimmer 31 in the light transmissive state and thepolarizing plate 3, and then reflected by thesecond dimmer 32 in the light reflective state. - When the
second panel 20 is to perform display, as shown inFIG. 10 , thefirst dimmer 31 is in the light reflective state and thesecond dimmer 32 is in the light transmissive state. Namely, thesecond panel 20 performs display using light which has been output from therear substrate 20 a of thesecond panel 20, passed through thesecond dimmer 32 in the light transmissive state and thepolarizing plate 3, and then reflected by thefirst dimmer 31 in the light reflective state. - In the liquid
crystal display device 200 in this preferred embodiment also, the rear substrate of each of the two liquid crystal display panels acts as a light guide plate. Therefore, as compared with the case where the backlight is used as shown inFIG. 16 , the entire thickness of the liquid crystal display device can be reduced by the thickness of the light guide plate, which is provided in the case ofFIG. 16 but not in this embodiment. In addition, onepolarizing plate 3 is shared by the two liquid crystal display panels, which can further reduce the thickness of the liquid crystal display device. - Furthermore, the
first dimmer 31 and the second dimmer are switched between the light transmissive state and the light reflective state in synchronization with the driving of thefirst panel 10 and thesecond panel 20. This allows the two panels to appear as being lit up at the same time. - Specifically usable for the
first dimmer 31 and thesecond dimmer 32 are electrochromic elements, the light reflectance of which is reversibly changed by a voltage application. An electrochromic element includes a dimmer layer formed of a material, the light reflectance of which is reversibly changed by electrochemical oxidation and reduction reactions, and a pair of transparent conductive layers for applying a voltage to the dimmer layer. The dimmer layer is, for example, a rare earth metal thin film of yttrium, lanthanum or the like, or a magnesium-nickel alloy thin film covered with palladium or the like. - An electrochromic element in the light reflective state specular-reflects light. For this reason, in order to prevent external light from being imaged or in order to enlarge the viewing angle, it is preferable to provide a light scattering element. For example, polarizing plates with a light scattering layer may be preferably used as the
polarizing plates dimmers - With reference to
FIG. 11 , a liquidcrystal display device 300 according to this preferred embodiment will be described. In the following, differences of the liquidcrystal display device 300 from the liquidcrystal display device 200 inPreferred Embodiment 2 will be mainly described. - In the liquid
crystal display device 300, as shown inFIG. 11 , thelight source 11 is provided to a side of therear substrate 10 a of thefirst panel 10, but no light source is provided to a side of therear substrate 20 a of thesecond panel 20. The dimmer 32 is provided between therear substrate 20 a of thesecond panel 20 and thepolarizing plate 3, but no dimmer is provided between therear substrate 10 a of thefirst panel 10 and thepolarizing plate 3. Therear substrate 10 a of thefirst panel 10 includes thelight guide layer 14 and the lowrefractive index layer 15, but therear substrate 20 a of thesecond panel 20 includes neither the light guide layer nor the low refractive index layer. - The liquid
crystal display device 300 in this preferred embodiment performs display as follows. - When the
first panel 10 is to perform display, as shown inFIG. 12 , thefirst dimmer 32 is in the light reflective state. Namely, thefirst panel 10 performs display using light which has been output from therear substrate 10 a of thefirst panel 10, passed through thepolarizing plate 3, and then reflected by the dimmer 32 in the light reflective state. - When the
second panel 20 is to perform display, as shown inFIG. 13 , the dimmer 32 is in the light transmissive state. Namely, thesecond panel 20 performs display using light which has been output from therear substrate 10 a of thefirst panel 10 and passed through thepolarizing plate 3 and the dimmer 32 in the light transmissive state. - In the liquid
crystal display device 300 in this preferred embodiment also, as compared with the case where the backlight is used as shown inFIG. 16 , the entire thickness of the liquid crystal display device can be reduced by the thickness of the light guide plate, which is provided in the case ofFIG. 16 but not in this embodiment. In addition, onepolarizing plate 3 is shared by the two liquid crystal display panels, which can further reduce the thickness of the liquid crystal display device. - Furthermore, in this preferred embodiment, the light source does not need to be provided to the side of the
rear substrate 20 a of thesecond panel 20, which can reduce the production cost. Therear substrate 20 a of thesecond panel 20 does not need to include a light guide layer or a low refractive index layer, which can further reduce the production cost. -
FIGS. 11 through 13 show thefirst panel 10 and thesecond panel 20 with substantially the same size (i.e., the display screens are shown with substantially the same size). Thesecond panel 20 may be smaller than (i.e., may have a smaller display screen than that of) thefirst panel 10 because therear substrate 20 a of thesecond panel 20 does not need to include a light guide layer. As understood from the above, in this preferred embodiment, thesecond panel 20 has a higher degree of designing freedom. - The dimmer 32 is switched between the light transmissive state and the light reflective state in synchronization with the driving of the
first panel 10 and thesecond panel 20. This allows the two panels to appear as being lit up at the same time. - A liquid crystal display device according to preferred embodiments of the present invention can have a reduced thickness and therefore is preferably usable for mobile phones.
FIGS. 14A and 14B andFIGS. 15A-15D show afoldable type phone 400 including a liquid crystal display device according to the present invention.FIGS. 14A and 14B show a folded state, whereinFIG. 14A is a side view andFIG. 14B is a front view.FIGS. 15A , 15B and 15C show an opened state, whereinFIG. 15A is a side view,FIG. 15B is a front view, andFIG. 15C is a rear view. - The
mobile phone 400 is a so-called two screen type mobile phone including amain display screen 60A for displaying main information and asub display screen 60B for displaying supplementary information. Thesub display screen 60B displays, for example, the radio wave receiving state, the remaining battery life or the like. - The
mobile phone 400 includes a liquid crystal display device according to any of the various preferred embodiments of the present invention (in the figures, the elements other than thefirst panel 10 and thesecond panel 20 are omitted) and a housing for accommodating various elements including the liquid crystal display device. - The housing includes a
display section 60 for accommodating the liquid crystal display device, anoperation section 70 includingoperation keys 71, and a connection section (e.g., a hinge) 80 for connecting thedisplay section 60 and theoperation section 70. The housing is foldable at theconnection section 80. Themobile phone 400 includes a liquid crystal display device according to any of the various preferred embodiments of the present invention in thedisplay section 60, and therefore can have a reduced thickness than the conventional mobile phones. - A liquid crystal display device according to preferred embodiments of the present invention can have a reduced thickness than the conventional mobile phones, and is preferably usable for various types of mobile electronic devices, especially preferably for foldable type mobile phones.
- While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.
Claims (6)
Priority Applications (1)
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US12/828,476 US7830475B1 (en) | 2005-10-04 | 2010-07-01 | Double sided liquid crystal display unit and portable electronic apparatus comprising a polarizing element between two liquid crystal display panels |
Applications Claiming Priority (5)
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JP2005-291217 | 2005-10-04 | ||
JP2005291217 | 2005-10-04 | ||
PCT/JP2006/318245 WO2007040028A1 (en) | 2005-10-04 | 2006-09-14 | Liquid crystal display unit and portable electronic apparatus provided with it |
US8908908A | 2008-04-03 | 2008-04-03 | |
US12/828,476 US7830475B1 (en) | 2005-10-04 | 2010-07-01 | Double sided liquid crystal display unit and portable electronic apparatus comprising a polarizing element between two liquid crystal display panels |
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PCT/JP2006/318245 Division WO2007040028A1 (en) | 2005-10-04 | 2006-09-14 | Liquid crystal display unit and portable electronic apparatus provided with it |
US12/089,089 Division US7796215B2 (en) | 2005-10-04 | 2006-09-14 | Double sided liquid crystal display unit and portable electronic apparatus comprising a polarizing element between two liquid crystal display panels |
US8908908A Division | 2005-10-04 | 2008-04-03 |
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US20100265438A1 true US20100265438A1 (en) | 2010-10-21 |
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US12/828,476 Expired - Fee Related US7830475B1 (en) | 2005-10-04 | 2010-07-01 | Double sided liquid crystal display unit and portable electronic apparatus comprising a polarizing element between two liquid crystal display panels |
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US12/089,089 Expired - Fee Related US7796215B2 (en) | 2005-10-04 | 2006-09-14 | Double sided liquid crystal display unit and portable electronic apparatus comprising a polarizing element between two liquid crystal display panels |
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US9436037B2 (en) * | 2014-06-20 | 2016-09-06 | Shenzhen China Star Optoelectronics Technology Co., Ltd | Double-sides liquid crystal devices and backlight modules |
CN104155791B (en) * | 2014-07-11 | 2017-01-18 | 京东方科技集团股份有限公司 | Double-sided display panel and double-sided display device |
JP6451979B2 (en) * | 2014-10-11 | 2019-01-16 | Tianma Japan株式会社 | Display element and portable information device using the same |
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KR102554120B1 (en) * | 2016-03-24 | 2023-07-12 | 티씨엘 차이나 스타 옵토일렉트로닉스 테크놀로지 컴퍼니 리미티드 | Liquid crystal display |
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Also Published As
Publication number | Publication date |
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US20090040422A1 (en) | 2009-02-12 |
WO2007040028A1 (en) | 2007-04-12 |
US7796215B2 (en) | 2010-09-14 |
US7830475B1 (en) | 2010-11-09 |
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