WO2015022879A1 - 液晶表示装置 - Google Patents
液晶表示装置 Download PDFInfo
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- WO2015022879A1 WO2015022879A1 PCT/JP2014/070588 JP2014070588W WO2015022879A1 WO 2015022879 A1 WO2015022879 A1 WO 2015022879A1 JP 2014070588 W JP2014070588 W JP 2014070588W WO 2015022879 A1 WO2015022879 A1 WO 2015022879A1
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- light
- liquid crystal
- display device
- selective reflection
- crystal display
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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
- G02F1/133553—Reflecting elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/20—Filters
- G02B5/26—Reflecting filters
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
-
- 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
- G02F1/133528—Polarisers
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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
- G02F1/133528—Polarisers
- G02F1/133536—Reflective polarizers
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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
- G02F1/133602—Direct backlight
- G02F1/133605—Direct backlight including specially adapted reflectors
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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
- G02F1/13362—Illuminating devices providing polarized light, e.g. by converting a polarisation component into another one
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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
- G02F1/133614—Illuminating devices using photoluminescence, e.g. phosphors illuminated by UV or blue light
Definitions
- the present invention relates to a liquid crystal display device. Specifically, the present invention relates to a liquid crystal display device with improved front luminance.
- Liquid crystal display devices (hereinafter also referred to as LCDs) have low power consumption and are increasingly used year by year as space-saving image display devices.
- the liquid crystal display device has a configuration in which a backlight (hereinafter also referred to as BL), a backlight side polarizing plate, a liquid crystal cell, a display side polarizing plate, and the like are provided in this order.
- BL backlight
- a backlight side polarizing plate a liquid crystal cell
- display side polarizing plate and the like
- an optical sheet member may be provided between the backlight and the backlight side polarizing plate in order to increase the light use efficiency.
- the optical sheet member is an optical element that transmits only light that vibrates in a specific polarization direction and reflects light that vibrates in other polarization directions among incident light that vibrates in all directions.
- Patent Document 1 A technique for improving the luminance while improving the efficiency and saving the power of the backlight is known (see Patent Document 1).
- Patent Document 2 describes a polarizing plate having a structure in which a ⁇ / 4 plate and a cholesteric liquid crystal phase are laminated.
- a layer formed by fixing three or more cholesteric liquid crystal phases having different pitches of cholesteric liquid crystal phases the light utilization efficiency of BL can be improved by light recycling.
- such an optical sheet member has a complicated member configuration, and in order to spread in the market, it is essential to reduce the cost by reducing the number of members by further integrating the functions of the members.
- Patent Document 3 realizes high brightness and improved color reproducibility by embodying white light using a quantum dot (QD) that emits red light and green light as a phosphor between a blue LED and a light guide plate. How to do is described.
- Non-Patent Document 1 proposes a method in which light conversion sheets (QDEF, also referred to as quantum dot sheets) using quantum dots are combined in order to improve the color reproducibility of the LCD.
- Patent Document 4 discloses that a phosphor layer including a phosphor made of quantum dots is disposed on a light path irradiated by a purple LED or a blue LED, thereby reducing energy loss in a color filter, and liquid crystal. Methods for increasing the energy efficiency of displays have been proposed.
- Patent Document 5 describes a bright ambient light condition with low power consumption by combining a blue light source, a cholesteric liquid crystal, a light conversion layer capable of changing the wavelength of light to a longer value, and a ⁇ / 4 plate.
- a liquid crystal display device has been proposed that provides a bright image with clear visibility and improved long-term reliability.
- Patent Documents 1 and 2 that improve the light utilization efficiency have a complex structure that takes into account the wavelength dispersion of the multi-layer configuration and members in order to give a broadband light recycling function to white light, There is a problem of high manufacturing costs.
- fluorescence (PL) applied technology shown in Patent Documents 3 and 4 and Non-Patent Document 1
- quantum dots Quantum Dot, hereinafter also referred to as QD
- realize high luminance and color reproducibility improvement for further luminance improvement, a combination with Patent Documents 1 and 2 is essential, and there are problems similar to Patent Documents 1 and 2.
- Patent Document 5 describes a light conversion member that emits polarized light by combining a cholesteric liquid crystal or a ⁇ / 4 plate and a light conversion member, but does not focus on improving the utilization efficiency of light that excites fluorescent light emission. There was a problem of improving the brightness. It is a problem to be solved by the present invention to provide a liquid crystal display device having a novel member configuration capable of improving the front luminance including improvement of the BL light utilization rate necessary for power saving. Another object of the present invention is to reduce the cost by reducing the number of members by further integrating the functions of the members.
- the problem to be solved by the present invention is to provide a liquid crystal display device with improved front luminance.
- a backlight unit, a light conversion member, a selective reflection member, a liquid crystal cell, and a display side polarizer are arranged in this order;
- the backlight unit includes a light source that emits non-polarized light having an emission center wavelength in a wavelength band of 300 nm or more and less than 430 nm;
- a selective reflection member reflects 60 to 100% of the non-polarized light incident on the selective reflection member and transmits at least a part of light in a wavelength band of more than 430 nm and not more than 650 nm;
- the light conversion member is caused by the aforementioned non-polarized light incident on the light conversion member.
- Blue light which is linearly polarized light having an emission center wavelength in the wavelength band of 430 to 480 nm and having a vibration direction parallel to the absorption axis of the display-side polarizer; Green light having a central emission wavelength in a wavelength band of 500 to 600 nm and linearly polarized light having a vibration direction parallel to the absorption axis of the display-side polarizer, and Red light which is linearly polarized light having an emission center wavelength in the wavelength band of 600 to 650 nm and having a vibration direction parallel to the absorption axis of the display-side polarizer; An oriented fluorescent material that emits light; Liquid crystal display device.
- the non-polarized light includes light in a first polarization state and light in a second polarization state;
- the selective reflection member includes a first selective reflection region and a second selective reflection region in order from the backlight side, The first selective reflection region reflects the light in the first polarization state out of the non-polarized light incident on the first selective reflection region, and the light in the second polarization state is polarized.
- the second selective reflection region reflects the light in the second polarization state that passes through the first selective reflection region and enters the second selective reflection region, and has a wavelength band greater than 430 nm and less than or equal to 650 nm. Is preferably transmitted.
- the selective reflection member includes a first dielectric multilayer film and a second dielectric multilayer film in this order,
- the first dielectric multilayer film has a reflection center wavelength in a wavelength band of 300 to 430 nm, reflects linearly polarized light in a first direction at the reflection center wavelength, and has a second direction orthogonal to the first direction.
- the selective reflection member has a light reflection layer in which the first cholesteric liquid crystal phase is fixed and light in which the second cholesteric liquid crystal phase is fixed.
- the light reflection layer formed by fixing the first cholesteric liquid crystal phase has a reflection center wavelength in the wavelength band of 300 to 430 nm, reflects one of right circularly polarized light and left circularly polarized light at the reflection center wavelength, and And transmits at least part of light in a wavelength band greater than 430 nm and less than or equal to 650 nm;
- the light reflection layer formed by fixing the second cholesteric liquid crystal phase has a reflection center wavelength in the wavelength band of 300 to 430 nm, and is different from the light reflection layer formed by fixing the first cholesteric liquid crystal phase at the reflection center wavelength.
- the liquid crystal display device has a backlight side polarizer between the selective reflection member and the liquid crystal cell, It is preferable that the absorption axes of the backlight side polarizer and the display side polarizer are orthogonal to each other.
- the liquid crystal display device has two polarizing plate protective films on both surfaces of the backlight side polarizer, Of the two polarizing plate protective films, at least the polarizing plate protective film on the selective reflection member side is preferably a cellulose acylate film.
- the fluorescent material preferably includes at least quantum dots.
- the quantum dots are ellipsoidal or rectangular parallelepiped quantum rods.
- the long axis direction of the quantum rod is preferably aligned in a direction parallel to the absorption axis of the display-side polarizer.
- the light conversion member is an oriented fluorescent sheet formed by stretching after dispersing the fluorescent material.
- the blue light emitted from the light conversion member, the green light, and the red light all have half widths. It preferably has an emission intensity peak of 100 nm or less.
- the entire backlight unit is preferably a surface light source.
- the emission center wavelength of the non-polarized light emitted from the backlight unit may be in a wavelength band of 300 to 380 nm. preferable.
- the non-polarized light emitted from the backlight unit has a peak of emission intensity with a half-value width of 30 nm or less. It is preferable.
- the backlight unit includes a reflective member capable of reflecting a part or all of light in a wavelength band of 300 to 430 nm. preferable.
- a liquid crystal display device with improved front luminance can be provided.
- FIG. 1 is a schematic view showing a cross section of an example of the liquid crystal display device of the present invention.
- FIG. 2 is a schematic view showing a cross section of another example of the liquid crystal display device of the present invention, in which the selective reflection member is not in contact with the liquid crystal cell.
- FIG. 3 is a schematic view showing a cross section of another example of the liquid crystal display device of the present invention, which has a configuration in which a backlight side polarizer is provided and a selective reflection member is in contact with the backlight side polarizer.
- FIG. 4 is a schematic view showing a cross section of another example of the liquid crystal display device of the present invention.
- the backlight unit further includes a reflecting member.
- FIG. 5 is a schematic view showing a cross-section of another example of the liquid crystal display device of the present invention, which has a configuration in which a backlight-side polarizer is provided and the selective reflection member is not in contact with the backlight-side polarizer. .
- a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
- the “half width” of a peak means the width of the peak at a peak height of 1/2.
- Non-polarized light is light that does not have polarization characteristics.
- a backlight unit In the liquid crystal display device of the present invention, a backlight unit, a light conversion member, a selective reflection member, a liquid crystal cell, and a display-side polarizer are arranged in this order;
- the backlight unit includes a light source that emits non-polarized light having an emission center wavelength in a wavelength band of 300 nm or more and less than 430 nm;
- a selective reflection member reflects 60 to 100% of the non-polarized light incident on the selective reflection member and transmits at least a part of light in a wavelength band of more than 430 nm and not more than 650 nm;
- the light conversion member is caused by the aforementioned non-polarized light incident on the light conversion member.
- Blue light which is linearly polarized light having an emission center wavelength in the wavelength band of 430 to 480 nm and having a vibration direction parallel to the absorption axis of the display-side polarizer; Green light having a central emission wavelength in a wavelength band of 500 to 600 nm and linearly polarized light having a vibration direction parallel to the absorption axis of the display-side polarizer, and Red light which is linearly polarized light having an emission center wavelength in the wavelength band of 600 to 650 nm and having a vibration direction parallel to the absorption axis of the display-side polarizer; An oriented fluorescent material that emits light.
- the front luminance of the liquid crystal display device of the present invention is improved, and the member thickness can be reduced by reducing the number of members.
- a selective reflection member that can reflect most of the light of the backlight in a part of the ultraviolet light to blue region and transmit visible light, and blue light when ultraviolet light to short wavelength blue light is incident.
- the backlight absorbs more light than the liquid crystal cell. And the light utilization rate can be increased.
- the transmission axis of the display-side polarizer is parallel to the vibration directions of the blue light, the green light, and the red light, any of the blue light, the green light, and the red light is selected. Even if there is no backlight side polarizing plate, the polarization state is uniform and can enter the liquid crystal cell.
- the liquid crystal display device 51 of the present invention shown in FIG. 1 includes a backlight unit 31, a light conversion member 16, a selective reflection member 5, a liquid crystal cell 42, and a display side polarizing plate 44.
- the backlight unit 31 includes a light source 31A that emits non-polarized light having an emission center wavelength in a wavelength band of 300 nm or more and less than 430 nm.
- the backlight unit 31 preferably includes a light guide plate 31B for use as a surface light source, a reflecting member 31C (FIGS. 4 to 5) that can reflect a part or all of light in the wavelength band of 300 to 430 nm.
- the selective reflection member 5 selectively reflects 60 to 100% of the non-polarized light 32 incident on the selective reflection member 5, and at least a part of light in a wavelength band greater than 430 nm and less than or equal to 650 nm (for example, light At least a part (preferably all) of the blue light 34 emitted by the conversion member, at least a part (preferably all) of the green light 35 emitted by the light conversion member, and at least a red light 36 emitted by the light conversion member Part (preferably all)) can be transmitted.
- the liquid crystal display device of the present invention may be configured not to include a later-described backlight-side polarizer 3 and a later-described backlight-side polarizing plate 1 as shown in FIGS. 1 and 2.
- the liquid crystal cell 42 and the selective reflection member 5 may be in direct contact with each other as shown in FIG. 1 or may be laminated via an adhesive layer (not shown). As shown in FIG.
- the selective reflection member 5 may be disposed separately from 42 (via an air layer).
- a specific configuration of the selective reflection member 5 a configuration having the first selective reflection region 5a and the second selective reflection region 5b shown in FIGS. 1 to 5 in this order from the backlight side is preferable.
- the first selective reflection region 5a a light reflection layer formed by fixing a dielectric multilayer film or a cholesteric liquid crystal phase can be used.
- the second selective reflection region 5b another dielectric multilayer film in which the direction of linearly polarized light that can be reflected from the dielectric multilayer film used in the first selective reflection region 5a is orthogonal, or the first selective reflection region 5a. It is possible to use a light reflecting layer formed by fixing a cholesteric liquid crystal phase in which the direction of circularly polarized light that can be reflected is opposite to the light reflecting layer formed by fixing the cholesteric liquid crystal phase used in the above.
- the selective reflection member 5 is not limited to the configuration shown in FIGS.
- the first dielectric multilayer film that is the first selective reflection region 5a and the second dielectric multilayer film that is the second selective reflection region 5a are provided in this order from the backlight side.
- the non-polarized light 32 incident on the selective reflection member 5 is reflected by linearly polarized light in the first direction at the reflection center wavelength when passing through the first selective reflection region 5a, and this first direction.
- the linearly polarized light in the second direction orthogonal to is transmitted through the first selective reflection region 5a.
- the linearly polarized light in the second direction that has passed through the first selective reflection region 5a is reflected by the second selective reflection region 5b.
- the linearly polarized light in the direction proceeds to the light conversion member 16 or the backlight unit 31.
- the first dielectric multilayer film which is the first selective reflection region 5a, has at least a part of light in a wavelength band of more than 430 nm and not more than 650 nm, specifically, linearly polarized light emitted by a light conversion member described later.
- the second dielectric multilayer film as the second selective reflection region 5b also has at least a part of light in a wavelength band of more than 430 nm and not more than 650 nm, specifically, linearly polarized blue light 34 emitted from a light conversion member described later.
- the linearly polarized blue light 34 emitted from the light conversion member incident on the second dielectric multilayer film which is the second selective reflection region 5b
- the green light 35 and the red light 36 also pass through the second selective reflection region 5b and travel toward the liquid crystal cell 42 or the optionally provided backlight-side polarizer 1.
- the selective reflection member 5 a light reflection layer formed by fixing the first cholesteric liquid crystal phase that is the first selective reflection region 5a and a second cholesteric liquid crystal phase that is the second selective reflection region 5a are provided.
- the non-polarized light 32 incident on the selective reflection member 5 is right at the reflection center wavelength when passing through the first selective reflection region 5a.
- One of circularly polarized light and left circularly polarized light is reflected and the other is transmitted.
- Circularly polarized light having a direction different from the direction reflected by the light reflecting layer formed by fixing the first cholesteric liquid crystal phase that has passed through the first selective reflection region 5a is reflected by the second selective reflection region 5b.
- the circularly polarized light in the other direction reflected by the light reflecting layer formed by fixing the cholesteric liquid crystal phase proceeds to the light conversion member 16 or the backlight unit 31.
- the light 33 reflected by the selective reflection member proceeding to the backlight unit 31, that is, the right circularly polarized light and the left circularly polarized light having a wavelength band of 300 nm or more and less than 430 nm, are arbitrary members constituting the backlight unit 31, for example, a light guide plate
- the light conversion member 16 or selective reflection is reflected or scattered as a retroreflected light 37 having a wavelength band of 300 nm or more and less than 430 nm by being reflected or scattered by the interface of 31B or the arbitrarily provided reflecting member 31C shown in FIG. 4 or FIG. Head for member 5.
- the light reflection layer formed by fixing the first cholesteric liquid crystal phase which is the first selective reflection region 5a is combined with at least a part of light in a wavelength band of more than 430 nm and not more than 650 nm, specifically described later. Since part or all of the linearly polarized blue light 34, green light 35, and red light 36 emitted from the light conversion member is transmitted, the first cholesteric liquid crystal phase that is the first selective reflection region 5a is fixed. The linearly polarized blue light 34, green light 35, and red light 36 emitted from the light conversion member that has passed through the light reflection layer travel to the second selective reflection region 5b.
- the light reflection layer formed by fixing the second cholesteric liquid crystal phase which is the second selective reflection region 5b, also emits at least part of light in a wavelength band of more than 430 nm and less than 650 nm, specifically, a light conversion member described later emits light. Since part or all of the linearly polarized blue light 34, green light 35, and red light 36 is transmitted, it is incident on the light reflection layer formed by fixing the second cholesteric liquid crystal phase as the second selective reflection region 5 b.
- the linearly polarized blue light 34, green light 35, and red light 36 emitted from the light conversion member that has passed through the second selective reflection region 5b pass through the liquid crystal cell 42 or the optionally provided backlight-side polarizer 1. Head for.
- the light conversion member 16 is a linearly polarized light having an emission center wavelength in a wavelength band of 430 to 480 nm and a vibration direction parallel to the absorption axis of the display-side polarizer by non-polarized light incident on the light conversion member 16.
- the fluorescent materials 17B, 17G, and 17R are arranged so as to emit red light 36 having a light emission center wavelength and linearly polarized light having a vibration direction parallel to the absorption axis of the display-side polarizer.
- Non-polarized light incident on the light conversion member 16 includes non-polarized light 32 having an emission center wavelength in a wavelength band of 300 nm or more and less than 430 nm emitted from the backlight unit; and an emission center in a wavelength band of 300 nm or more and less than 430 nm.
- the backlight side polarizer 3 that may be optionally provided as shown in FIGS. 3 to 5 has the transmission axis (not shown) of the backlight side polarizer 3 having the blue light 34, the green light 35, and It is preferable to be arranged so as to be parallel to the vibration direction of the red light 36 described above. Moreover, it is preferable that the absorption axis of the backlight side polarizer 3 and the display side polarizer 46 is orthogonal, that is, the transmission axis of the backlight side polarizer 3 and the display side polarizer 46 is orthogonal.
- a structure in which a polarizing plate protective film is laminated on at least one surface of the backlight side polarizer 3 is referred to as a backlight side polarizing plate 1, and the configuration of the backlight side polarizing plate is not particularly limited and has a known configuration.
- it can be set as the structure of the laminated body of the polarizing plate protective film (inner side) 2, the polarizer 3, and the polarizing plate protective film (outer side) 4.
- FIG. Further, for example, an innerless configuration in which a polarizing plate protective film is not provided on the inner side but an adhesive or a coating film is provided directly on the polarizer can be employed.
- the selective reflection member 5 described above can be used as the outer polarizing plate protective film or instead of the outer polarizing plate protective film 4. That is, the selective reflection member 5 can also serve as the outer polarizing plate protective film 4 included in the backlight side polarizing plate.
- the selective reflection member 5 and the backlight side polarizer 3 may be arranged directly or adjacent to each other via an adhesive layer (not shown) or the polarizing plate protective film 4 on the outer side. (Refer FIG. 3 and FIG. 4), You may arrange
- the selective reflection member 5 and the backlight side polarizing plate 1 are disposed adjacent to each other via the outer side polarizing plate protective film 4 so that the optical performance of the selective reflection member 5 is accurate.
- the absorption axis of the display-side polarizer 46 is parallel to the vibration directions of the blue light 34, the green light 35, and the red light 36 described above.
- the display-side polarizing plate 44 including the display-side polarizer 46 is not particularly limited, and a known configuration can be adopted.
- a polarizing plate protective film (outer side) 45 It can be set as the structure of the laminated body of the display side polarizer 46 and the polarizing plate protective film (inner side) 47.
- a brightness enhancement film (not shown) may be further disposed between the light conversion member 16 and the selective reflection member 5, and as this brightness enhancement film, a known prism sheet or diffusion plate may be used. Can be mentioned.
- the arrangement position of the brightness enhancement film is not limited, and may be arranged between the light conversion member 16 and the backlight unit 31.
- the backlight unit includes a light source that emits non-polarized light having an emission center wavelength in a wavelength band of 300 nm or more and less than 430 nm.
- the backlight may be of an edge light type using a light guide plate, a reflection plate, or the like as a constituent member, or may be a direct type.
- the liquid crystal display device of the present invention has the entire backlight unit as a surface light source.
- the backlight unit when the backlight unit is of a light source or an edge light type, the light that is emitted from the light source and reflected by the selective reflection member is reflected at the rear part of the light guide plate (repetitive retroreflection). It is preferable to provide a member.
- the reflection member only needs to improve the brightness of the liquid crystal display device, and the polarization state of the light emitted from the light source and reflected by the selective reflection member is recirculated with its direction and polarization state randomized. There may be.
- the light source of the backlight unit preferably includes a UV light emitting diode or a blue light emitting diode that emits light having an emission center wavelength in the wavelength band of 300 nm or more and less than 430 nm. It is more preferable to have.
- the backlight unit preferably includes a known diffusion plate, diffusion sheet, prism sheet (for example, BEF).
- a known diffusion plate, diffusion sheet, prism sheet for example, BEF.
- Other members are also described in Japanese Patent No. 3416302, Japanese Patent No. 3363565, Japanese Patent No. 4091978, Japanese Patent No. 3448626, and the contents of these publications are incorporated in the present invention.
- the emission center wavelength of non-polarized light (ultraviolet light, violet light or short-wave blue light) emitted from the backlight unit is preferably in the wavelength band of 300 to 380 nm, and preferably 350 to 380 nm. More preferably, it is in the wavelength band.
- the non-polarized light emitted from the backlight unit preferably has a peak of emission intensity with a half width of 100 nm or less, and has a peak of emission intensity with a half width of 80 nm or less.
- the emission center wavelength of non-polarized light emitted from the backlight unit matches the reflection center wavelength of the selective reflection member. Specifically, it is preferable that the emission center wavelength of non-polarized light emitted from the backlight unit matches the reflection center wavelengths of the first selective reflection region and the second selective reflection region included in the selective reflection member. .
- the emission center wavelength of non-polarized light emitted from the backlight unit, the reflection center wavelength of the first dielectric multilayer film used as the first selective reflection region, and the second selective reflection region It is preferable that the reflection center wavelength of the second dielectric multilayer film used as a match.
- the emission center wavelength of the non-polarized light emitted from the backlight unit, the reflection center wavelength of the light reflection layer formed by fixing the first cholesteric liquid crystal phase used as the first selective reflection region, and the second It is preferable that the reflection center wavelength of the light reflection layer formed by fixing the second cholesteric liquid crystal phase used as the selective reflection region matches.
- “matching” two wavelengths is not limited to the case where the two wavelengths are completely matched, and the two wavelengths have an optically acceptable deviation. This includes cases where The difference between the emission center wavelength of non-polarized light emitted from the backlight unit and the reflection center wavelength of the selective reflection member is preferably within 50 nm, more preferably within 20 nm, and within 10 nm. Is particularly preferred.
- the emission center wavelength means a wavelength at which the peak of the spectrum of emission intensity takes the maximum value.
- the reflection center wavelength means a wavelength at which the peak of the reflectance spectrum takes a maximum value.
- the liquid crystal display device of the present invention includes a light conversion member, and has the emission center wavelength in the wavelength band of 430 to 480 nm by the above-described non-polarized light incident on the light conversion member, and the absorption axis of the display-side polarizer.
- Blue light that is linearly polarized light in a vibration direction parallel to the light; green light that has a central emission wavelength in the wavelength band of 500 to 600 nm and is linearly polarized light in a vibration direction parallel to the absorption axis of the display-side polarizer; and It includes an oriented fluorescent material that emits red light having a central emission wavelength in a wavelength band of 600 to 650 nm and linearly polarized light having a vibration direction parallel to the absorption axis of the display-side polarizer.
- the liquid crystal display device of the present invention is characterized in that the light conversion member includes a fluorescent material in which the light conversion member is oriented in order to emit linearly polarized light, that is, the light conversion member is oriented.
- the polarization state of the light emitted from the light conversion member can be measured, for example, by measuring the polarization with an Axoscan from Axometrics.
- the blue light, the green light, and the red light emitted from the light conversion member have a light emission intensity peak with a half width of 100 nm or less. It is more preferable to have an emission intensity peak with a value width of 80 nm or less, and particularly preferable to have an emission intensity peak with a half width of 70 nm or less.
- Inorganic fluorescent materials include yttrium / aluminum / garnet yellow phosphors and terbium / aluminum / garnet yellow phosphors.
- the fluorescence wavelength of the fluorescent material can be controlled by changing the particle diameter of the phosphor.
- fluorescent materials described in JP-T-2010-532005 can be used.
- Organic fluorescent materials can also be used.
- the fluorescent materials described in JP-A Nos. 2001-174636 and 2001-174809 can be used.
- a light conversion member having an organic or inorganic fluorescent material for example, a dye or a pigment, a sheet in which these fluorescent materials are oriented, a thermoplastic film formed by dispersing these fluorescent materials, or these It is preferably an adhesive layer in which a fluorescent material is dispersed and oriented.
- the quantum dots contained in the light conversion member are preferably quantum rods in which ellipsoidal or rectangular parallelepiped particles are oriented.
- Such an ellipsoidal or rectangular parallelepiped quantum rod is not particularly limited, and is not limited in U.S. Pat. No. 7,303,628, paper (Peng, XX; Manna, L .; Yang, WD; Wickham, j .; Kadavanich, A .; Alivisatos, A. P. Nature 2000, 404, 59-61) and articles (Manna, L .; Scher, E. C .; Alivitas, A. P. j. Am. Chem. Soc.
- the long axis direction of the quantum rod is aligned in a direction parallel to the transmission axis of the backlight side polarizer, depending on the vibration direction of the linearly polarized light of the incident light to the light conversion member.
- the light conversion member having the fluorescent material described above can use a thermoplastic film that is stretched after the quantum rod material is dispersed.
- thermoplastic film is not particularly limited, and a known one is used. However, it is described in, for example, Japanese Patent Application Laid-Open Nos. 2001-174636 and 2001-174809, and the contents of these documents are incorporated in the present invention.
- the front luminance can be sufficiently improved even if the amount of the fluorescent material contained in the light conversion member is small.
- the preferable range of the content of the fluorescent material contained in the light conversion member described above depends on the type of the fluorescent material. For example, the following content reduces the usage amount of the fluorescent material and lowers the manufacturing cost. It is preferable from the viewpoint. On the other hand, if the content is too small, the emission intensity is uneven in the plane of the light conversion member, which is not preferable.
- the above-mentioned fluorescent material is a quantum rod, it is preferable that the above-mentioned light conversion member is contained in the following content.
- the quantum rod mass per unit area is preferably in the range of 0.000001-2 g / m 2 , more preferably in the range of 0.000005-0.02 g / m 2 , and 0.00001-0. Most preferably, it is in the range of 01 g / m 2 .
- the selective reflection member described above reflects 60 to 100% of non-polarized light incident on the selective reflection member, and at least a part of light in a wavelength band of more than 430 nm and less than 650 nm. Transparent. That is, it selectively reflects the non-polarized light having the emission center wavelength in the wavelength band of 300 nm or more and less than 430 nm emitted from the backlight unit, or the light retroreflected by the backlight unit. It is preferable that the reflection function is not exhibited with respect to at least part of light in the wavelength band exceeding 650 nm.
- Non-polarized light having a wavelength band of 300 nm or more and less than 430 nm incident on the selective reflection member is only one kind of a known dielectric multilayer film (trade name DBEF, manufactured by 3M Company). It cannot be achieved in a mode in which it is used or only one type of light reflecting layer formed by fixing a cholesteric liquid crystal is used.
- the light reflecting layer formed by fixing these dielectric multilayer films and cholesteric liquid crystal reflects only one component of linearly polarized P wave and S wave, or one component of right circularly polarized light and left circularly polarized light. Even if only one type is used, the reflectance is only 50% at most.
- the selective reflection member described above preferably reflects 80 to 100% of non-polarized light having a wavelength band of 300 nm or more and less than 430 nm incident on the selective reflection member, and more preferably reflects 90 to 100%. It is particularly preferable to reflect 95 to 100%, and it is particularly preferable to reflect 99 to 100%.
- the selective reflection member has a reflection center wavelength in the wavelength band of 300 to 430 nm, the reflection center wavelength is preferably in the wavelength band of 300 to 380 nm, and more preferably in the wavelength band of 350 to 380 nm.
- the reflectance peak having a reflection center wavelength in the wavelength band of 300 to 430 nm is preferably a reflectance peak having a half width of 100 nm or less, and is preferably a reflectance peak having a half width of 80 nm or less. More preferably, it is a reflectance peak having a half width of 70 nm or less, more preferably a reflectance peak having a half width of 20 nm or less, and a reflectance peak having a half width of 10 nm or less. Even more preferred is a peak.
- the selective reflection member transmits at least a part of light in the wavelength band exceeding 430 nm and not more than 650 nm is not limited to an aspect in which the transmittance is 100% in the entire wavelength band exceeding 430 nm and not more than 650 nm.
- the transmittance at a desired wavelength in the wavelength band exceeding 430 nm and not more than 650 nm is only required to be optically acceptable in the liquid crystal display device.
- the selective reflection member described above does not have a reflectance peak in the visible light region other than the reflectance peak in the wavelength band of 300 nm or more and less than 430 nm.
- the selective reflection member described above is linearly polarized light having an emission center wavelength in the wavelength band of 430 to 480 nm emitted from the light conversion member and having a vibration direction parallel to the absorption axis of the display-side polarizer. It is preferable to transmit at least a part of the blue light, more preferably to transmit the light having the emission center wavelength of the blue light, and it is particularly preferable to transmit all of the emission peak of the blue light.
- the selective reflection member described above preferably has a maximum reflectance peak of 20% or less in the wavelength band of 430 to 480 nm, and has a maximum reflectance peak of 10% or less in the wavelength band of 430 to 480 nm.
- the maximum reflectance peak is 5% or less in the wavelength band of 430 to 480 nm.
- the selective reflection member described above has a light emission center wavelength in a wavelength band of 500 to 600 nm emitted from the light conversion member and is linearly polarized light having a vibration direction parallel to the absorption axis of the display-side polarizer. It is preferable to transmit at least a part of the above, more preferably transmit the light having the above-described green light emission center wavelength, and particularly preferably transmit all of the above-described green light emission peak.
- the selective reflection member described above preferably has a maximum reflectance peak of 20% or less in a wavelength band of 500 to 600 nm, and a maximum reflectance peak of 10% or less in a wavelength band of 500 to 600 nm. It is more preferable that the maximum reflectance peak is 5% or less in the wavelength band of 500 to 600 nm.
- the selective reflection member described above has at least a light emission center wavelength in a wavelength band of 600 to 650 nm emitted from the light conversion member, and at least red light that is linearly polarized light in a vibration direction parallel to the absorption axis of the display side polarizer.
- the selective reflection member described above preferably has a maximum reflectance peak of 20% or less in the wavelength band of 600 to 650 nm, and has a maximum reflectance peak of 10% or less in the wavelength band of 600 to 650 nm. More preferably, the maximum reflectance peak is 5% or less in the wavelength band of 600 to 650 nm.
- the selective reflection member described above has a polarization state of light having a wavelength band exceeding 430 nm and not more than 650 nm incident on the selective reflection member and a polarization state of light having a wavelength band exceeding 430 nm and not more than 650 nm emitted from the selective reflection member. It is preferable that they are substantially the same. Specifically, the vibration direction of linearly polarized light having a wavelength band exceeding 430 nm and not exceeding 650 nm incident on the selective reflection member and exceeding 430 nm and not exceeding 650 nm are emitted from the selective reflection member. It is preferable that the vibration directions of the linearly polarized light in the wavelength band are parallel.
- the polarization state of the light incident on the selective reflection member and the emitted light is substantially the same, the light exceeding the 430 nm incident on the selective reflection member while passing through the selective reflection member will be exceeded.
- the polarization state of light having a wavelength band of 650 nm or less may change.
- two ⁇ / 4 plates having slow axes orthogonal to each other may be passed through the selective reflection member described above.
- the total thickness of the selective reflection member is preferably 1 to 130 ⁇ m, more preferably 1 to 70 ⁇ m, particularly preferably 1 to 10 ⁇ m, and particularly preferably 1 to 8 ⁇ m.
- the selective reflection member described above has the first dielectric multilayer film and the second dielectric multilayer film in this order, and the first dielectric multilayer film is 300. It has a reflection center wavelength in the wavelength band of ⁇ 430 nm, reflects linearly polarized light in the first direction at the reflection center wavelength, and transmits linearly polarized light in the second direction orthogonal to the first direction, and exceeds 430 nm.
- the second dielectric multilayer film has a reflection center wavelength in a wavelength band of 300 to 430 nm, and the straight line in the second direction described above at the reflection center wavelength It is preferable to reflect polarized light and transmit at least part of light in a wavelength band of more than 430 nm and not more than 650 nm.
- the dielectric multilayer film used in this mode (i) reflects or transmits (emits) linearly polarized light with respect to unpolarized light having a wavelength band of 300 to 430 nm incident on the dielectric multilayer film.
- the aspect (i) includes a case where one of the wavelength bands of 300 to 430 nm has one reflectance peak that is substantially constant and flat with respect to the wavelength in all wavelength bands.
- the first selective reflection region 5a or the second selective reflection region 5b is drawn as a single layer for convenience of drawing, but the dielectric multilayer film used in the present invention is like this.
- the number of laminated dielectric multilayer films can be changed as appropriate in order to achieve the desired reflectance and reflection center wavelength.
- a first central light having a reflection center wavelength in a wavelength band of 300 to 430 nm, reflecting linearly polarized light in a first direction at the reflection center wavelength, and transmitting linearly polarized light in a second direction orthogonal to the first direction.
- a combination of the dielectric multilayer film and the second dielectric multilayer film having a reflection center wavelength in the wavelength band of 300 to 430 nm and reflecting the linearly polarized light in the second direction at the reflection center wavelength is not particularly limited. No.
- the same dielectric multilayer film as the first dielectric multilayer film can be used as the second dielectric multilayer film by laminating the first dielectric multilayer film by rotating 90 ° with respect to the first dielectric multilayer film.
- the dielectric multilayer film is preferably thinner.
- the total film thickness of all the dielectric multilayer films including the first dielectric multilayer film and the second dielectric multilayer film is preferably 5 to 100 ⁇ m, more preferably 5 to 50 ⁇ m, It is particularly preferably 5 to 20 ⁇ m, more particularly preferably 5 to 10 ⁇ m, still more preferably 5 to 9 ⁇ m.
- dielectric multilayer films Three or more kinds may be combined, but it is preferable to use only the first dielectric multilayer film and the second dielectric multilayer film from the viewpoint of reducing the total thickness of the selective reflection member. It is preferable not to have other dielectric multilayer films.
- the reflection center wavelength that is, the wavelength that gives the peak of the reflectance can be adjusted by changing the thickness or refractive index of each layer constituting the dielectric multilayer film.
- the paper Journal of Display Technology, Vol. 5, no. 8, (2009) “Design Optimization of Reflexive Polarizers for LCD Backlight Recycling” has a detailed description.
- the dielectric multilayer film may be referred to as a dielectric multilayer reflective polarizing plate or a birefringence interference polarizer having an alternating multilayer film.
- a first central light having a reflection center wavelength in a wavelength band of 300 to 430 nm, reflecting linearly polarized light in a first direction at the reflection center wavelength, and transmitting linearly polarized light in a second direction orthogonal to the first direction.
- a method of laminating the dielectric multilayer film and the second dielectric multilayer film having a reflection center wavelength in the wavelength band of 300 to 430 nm and reflecting the linearly polarized light in the second direction at the reflection center wavelength is particularly limited. There is no.
- the same dielectric multi-layer film as the first dielectric multi-layer film is rotated by 90 ° from the first dielectric multi-layer film and laminated to form a second dielectric multi-layer film. It can be set as the light reflection member of this invention by bonding together with an adhesive agent or an adhesive material.
- the selective reflection member includes a light reflection layer formed by fixing the first cholesteric liquid crystal phase and a light reflection layer formed by fixing the second cholesteric liquid crystal phase.
- the light reflecting layer having the first cholesteric liquid crystal phase fixed in this order has a reflection center wavelength in a wavelength band of 300 to 430 nm, and reflects one of right circular polarization and left circular polarization at the reflection center wavelength.
- a light reflection layer formed by fixing the second cholesteric liquid crystal phase has a wavelength band of 300 to 430 nm. Reflects circularly polarized light in a direction different from that of the light reflection layer having a reflection center wavelength and fixing the first cholesteric liquid crystal phase at the reflection center wavelength, and exceeding 430 nm and not more than 650 nm It is preferable to transmit at least part of the light of the long band.
- the light reflecting layer formed by fixing the cholesteric liquid crystal phase used in the embodiment (ii) is used for non-polarized light having a wavelength band of 300 to 430 nm incident on the light reflecting layer formed by fixing the cholesteric liquid crystal phase. , One of right circularly polarized light and left circularly polarized light is reflected or transmitted (emitted).
- wavelength bands of 300 to 430 nm there is one reflectance peak that is substantially constant in some wavelength bands (for example, 360 to 400 nm), the maximum value is flat with respect to the wavelength, and the rise is steep, and other wavelengths (
- a light reflecting layer formed by fixing a cholesteric liquid crystal phase having a reflection spectrum such that the reflectance is 0% in 300 to 360 nm or 400 to 430 nm is also included in this embodiment (ii).
- the film thickness is preferably 5 to 24 ⁇ m, more preferably 5 to 10 ⁇ m, and particularly preferably 5 to 9 ⁇ m.
- Three or more light reflecting layers formed by fixing the cholesteric liquid crystal phase may be combined. From the viewpoint of reducing the total film thickness of the selective reflection member, the light formed by fixing the first cholesteric liquid crystal phase. It is preferable to use only the light reflection layer formed by fixing the reflective layer and the second cholesteric liquid crystal phase, and it is preferable not to have a layer formed by fixing other cholesteric liquid crystal phases.
- the reflection center wavelength that is, the wavelength that gives the peak of the reflectance can be adjusted by changing the pitch or refractive index of the light reflecting layer formed by fixing the cholesteric liquid crystal phase. It can be easily adjusted by changing Specifically, Fujifilm research report No. 50 (2005) pp. There is a detailed description in 60-63.
- a first central light having a reflection center wavelength in a wavelength band of 300 to 430 nm, reflecting linearly polarized light in a first direction at the reflection center wavelength, and transmitting linearly polarized light in a second direction orthogonal to the first direction.
- stacking method of the light reflection layer fixed For example, a second cholesteric liquid crystal phase using a left-turning chiral agent is fixed on a light reflection layer formed by fixing a first cholesteric liquid crystal phase using a right-turning chiral agent.
- the light reflecting member of the present invention can be obtained by applying a light reflecting layer and drying and curing as necessary.
- cholesteric liquid crystal an appropriate one may be used and there is no particular limitation.
- the use of a liquid crystal polymer is advantageous from the standpoints of the superimposition efficiency of the liquid crystal layer and the thinning.
- a cholesteric liquid crystal molecule having a large birefringence is preferable because the wavelength range of selective reflection is widened.
- liquid crystal polymers examples include main chain type liquid crystal polymers such as polyester, side chain type liquid crystal polymers composed of acrylic main chain, methacryl main chain, siloxane main chain, etc., nematic liquid crystal polymers containing low molecular chiral agents, and introduction of chiral components. Any suitable liquid crystal polymer, nematic and cholesteric mixed liquid crystal polymer may be used. A glass transition temperature of 30 to 150 ° C. is preferable from the viewpoint of handleability.
- Formation of the light reflecting layer formed by fixing the cholesteric liquid crystal phase can be applied to the support directly from an appropriate orientation film such as polyimide, polyvinyl alcohol, or an obliquely deposited layer of SiO, or a transparent film. It can carry out by appropriate methods, such as the method of apply
- the support one having a phase difference as small as possible can be preferably used from the viewpoint of preventing the change of the polarization state. Further, a superposition method of a light reflection layer in which a cholesteric liquid crystal phase is fixed via an alignment film can also be adopted.
- the liquid crystal polymer can be applied by a method in which a liquid material such as a solvent solution or a molten liquid is heated by an appropriate method such as a roll coating method, a gravure printing method, or a spin coating method. .
- the thickness of the cholesteric liquid crystal layer to be formed is preferably 0.5 to 100 ⁇ m from the viewpoints of selective reflectivity, orientation disorder and prevention of transmittance decrease.
- the selective reflection member and the liquid crystal cell or the backlight side polarizer are arranged directly adjacent to each other via an adhesive layer or a polarizing plate protective film.
- the first selective reflection region and the second selective reflection region are preferably laminated in this order in direct contact or via an adhesive layer.
- Member integration reduces the thickness of the member, reduces interface reflection loss in the air space between the members, and eliminates display defects due to foreign matter mixing between members that may occur during or after the manufacture of a liquid crystal display device. Can do.
- a known method can be used as a method for bonding these members.
- a light reflection layer formed by fixing the cholesteric liquid crystal phase provided on the temporary support is laminated on the liquid crystal cell and the backlight side polarizer, and the temporary support is peeled off as necessary. It is preferable to form the selective reflection member described above.
- a roll-to-panel manufacturing method can be used, which is preferable for improving productivity and yield. The roll-to-panel manufacturing method is described in JP2011-48381, JP2009-175653, JP4628488, JP4729647, WO2012 / 014602, WO2012 / 014571, and the like. It is not limited.
- an adhesive layer may be disposed between these members.
- the pressure-sensitive adhesive that can be used in the present invention include, but are not limited to, acrylic pressure-sensitive adhesives and polyvinyl alcohol-based adhesives.
- Examples of the pressure-sensitive adhesive used for the above-described adhesive layer include resins such as polyester resins, epoxy resins, polyurethane resins, silicone resins, and acrylic resins. You may use these individually or in mixture of 2 or more types.
- an acrylic resin is preferable because it is excellent in reliability such as water resistance, heat resistance, and light resistance, has good adhesion and transparency, and can easily adjust the refractive index to be compatible with a liquid crystal display.
- acrylic pressure-sensitive adhesive acrylic acid and its esters, methacrylic acid and its esters, acrylamide, homopolymers of acrylic monomers such as acrylonitrile, or copolymers thereof, and at least one of the aforementioned acrylic monomers, Examples thereof include copolymers with aromatic vinyl monomers such as vinyl acetate, maleic anhydride, and styrene.
- main monomers such as ethylene acrylate, butyl acrylate, and 2-ethylhexyl acrylate that exhibit adhesiveness
- monomers such as vinyl acetate, acrylonitrile, acrylamide, styrene, methacrylate, and methyl acrylate that are cohesive components
- adhesion Functional group containing methacrylic acid, acrylic acid, itaconic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, acrylamide, methylol acrylamide, glycidyl methacrylate, maleic anhydride, etc.
- the curing agent for example, a metal chelate-based, isocyanate-based, or epoxy-based crosslinking agent is used, if necessary, or a mixture of two or more. It is practically preferable that such an acrylic pressure-sensitive adhesive is blended so as to have an adhesive strength in the range of 100 to 2000 g / 25 mm in a state of containing a filler to be described later. If the adhesive strength is less than 100 g / 25 mm, the environmental resistance is poor, and in particular, there is a risk of peeling at high temperature and high humidity. Problem arises.
- the refractive index of the acrylic pressure-sensitive adhesive (Method B according to JIS K-7142) is preferably in the range of 1.45 to 1.70, particularly preferably in the range of 1.5 to 1.65.
- the adhesive contains a filler for adjusting the refractive index.
- Fillers include inorganic white pigments such as silica, calcium carbonate, aluminum hydroxide, magnesium hydroxide, clay, talc, and titanium dioxide, and organic transparent or white such as acrylic resin, polystyrene resin, polyethylene resin, epoxy resin, and silicone resin. A pigment etc. can be mention
- an acrylic pressure-sensitive adhesive silicon beads and epoxy resin beads are preferable because they are excellent in dispersibility with respect to the acrylic pressure-sensitive adhesive and provide a uniform and good refractive index.
- the filler is preferably a spherical filler with uniform light diffusion.
- the particle size (JIS B9921) of such a filler is in the range of 0.1 to 20.0 ⁇ m, preferably 1.0 to 10.0 ⁇ m. In particular, the range of 0.5 to 10 ⁇ m is preferable.
- the refractive index of the filler (Method B according to JIS K-7142) preferably has a difference of 0.05 to 0.5, more preferably 0.05 to 0.3, with respect to the refractive index of the adhesive. .
- the filler content in the diffusion adhesive layer is preferably 1.0 to 40.0% by mass, and particularly preferably 3.0 to 20% by mass.
- the polarizing plate of the liquid crystal display device of the present invention preferably includes a polarizer and a polarizing plate protective film disposed on either side of the polarizer, and protects the polarizer and two polarizing plates disposed on both sides thereof. More preferably, it is made of a film (hereinafter also referred to as a protective film), but the above-mentioned selective reflection member may be used as the polarizing plate protective film on the outer side of the backlight side polarizing plate, and the inner side of the backlight side polarizing plate.
- the polarizing plate protective film may not be used.
- the present invention protects the film to make it thinner. It is preferable to make the film thinner (60 ⁇ m or less, preferably 40 ⁇ m or less, more preferably 25 ⁇ m or less). It is more preferable to use a hard coat (20 ⁇ m or less, preferably 10 ⁇ m or less, more preferably 5 ⁇ m or less) coated, dried and cured with a protective resin such as an acrylic resin. The use of a polarizer without a protective layer is more preferable for realizing a thinner film.
- a retardation film is used in the case of a VA, IPS, TN, OCB mode liquid crystal display device.
- the IPS mode it is preferable to use an optical compensation film having substantially no phase difference, and it is preferable not to use a polarizing plate protective film on the inner side for realizing a thinner film.
- polarizer As the above-mentioned polarizer, it is preferable to use a polymer film in which iodine is adsorbed and oriented.
- the polymer film is not particularly limited, and various types can be used.
- polyvinyl alcohol films, polyethylene terephthalate films, ethylene / vinyl acetate copolymer films, partially saponified films of these, hydrophilic polymer films such as cellulose films, polyvinyl alcohol dehydrated products and polychlorinated Examples include polyene-based oriented films such as vinyl dehydrochlorinated products.
- the polyvinyl alcohol film is made of polyvinyl alcohol or a derivative thereof.
- Derivatives of polyvinyl alcohol include polyvinyl formal, polyvinyl acetal and the like, olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, alkyl esters thereof, acrylamide and the like. can give.
- the polymerization degree of the polymer that is the material of the polymer film is generally 500 to 10,000, preferably in the range of 1000 to 6000, and more preferably in the range of 1400 to 4000. Furthermore, in the case of a saponified film, the degree of saponification is preferably 75 mol% or more, more preferably 98 mol% or more, for example, from the viewpoint of solubility in water, and more preferably 98.3 to 99.8 mol. % Is more preferable.
- the aforementioned polymer film (unstretched film) is at least subjected to uniaxial stretching treatment and iodine dyeing treatment according to a conventional method. Furthermore, boric acid treatment and washing treatment can be performed. Further, the polymer film (stretched film) subjected to the above-described treatment is dried according to a conventional method to become a polarizer.
- the stretching method in the uniaxial stretching process is not particularly limited, and either a wet stretching method or a dry stretching method can be employed.
- the stretching means of the dry stretching method include an inter-roll stretching method, a heated roll stretching method, and a compression stretching method. Stretching can also be performed in multiple stages.
- the unstretched film is usually heated.
- the stretch ratio of the stretched film can be appropriately set according to the purpose, but the stretch ratio (total stretch ratio) is about 2 to 8 times, preferably 3 to 7 times, more preferably 3.5 to 6.5 times. Is desirable.
- the iodine staining treatment is performed, for example, by immersing the polymer film in an iodine solution containing iodine and potassium iodide.
- the iodine solution is usually an iodine aqueous solution, and contains iodine and potassium iodide as a dissolution aid.
- the iodine concentration is about 0.01 to 1% by mass, preferably 0.02 to 0.5% by mass, and the potassium iodide concentration is about 0.01 to 10% by mass, and further 0.02 to 8% by mass. It is preferable to use it.
- the temperature of the iodine solution is usually about 20 to 50 ° C., preferably 25 to 40 ° C.
- the immersion time is usually about 10 to 300 seconds, preferably 20 to 240 seconds.
- the iodine dyeing treatment the iodine content and potassium content in the polymer film are adjusted to the above-mentioned ranges by adjusting the conditions such as the concentration of the iodine solution, the immersion temperature of the polymer film in the iodine solution, and the immersion time. To do.
- the iodine dyeing process may be performed at any stage before the uniaxial stretching process, during the uniaxial stretching process, or after the uniaxial stretching process.
- the iodine content of the above-mentioned polarizer is, for example, in the range of 2 to 5% by mass, preferably in the range of 2 to 4% by mass in consideration of optical characteristics.
- the aforementioned polarizer preferably contains potassium.
- the potassium content is preferably in the range of 0.2 to 0.9% by mass, more preferably in the range of 0.5 to 0.8% by mass.
- a polarizing film having a preferable composite elastic modulus (Er) and a high degree of polarization can be obtained.
- the potassium can be contained, for example, by immersing a polymer film, which is a material for forming a polarizer, in a solution containing potassium.
- the aforementioned solution may also serve as a solution containing iodine.
- drying treatment step a conventionally known drying method such as natural drying, blow drying, or heat drying can be used.
- the heating temperature is about 20 to 80 ° C.
- the drying time is about 1 to 10 minutes.
- stretch suitably also in this drying process process.
- the thickness of the polarizer is not particularly limited, and is usually 1 to 100 ⁇ m, preferably 3 to 30 ⁇ m, more preferably 5 to 20 ⁇ m.
- the single transmittance when measured with a single polarizer is preferably 43% or more, and more preferably in the range of 43.3 to 45.0%. Further, it is preferable that the orthogonal transmittance measured by superposing two polarizers described above so that the absorption axes of the two polarizers are 90 ° with each other is smaller, and practically 0.00 % Or more and 0.050% or less is preferable, and 0.030% or less is more preferable.
- the degree of polarization is preferably 99.90% or more and 100% or less for practical use, and particularly preferably 99.93% or more and 100% or less. Even when measured as a polarizing plate, it is preferable to obtain optical characteristics substantially equivalent to this.
- thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is used.
- thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth) acrylic resins, cyclic Examples thereof include polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof.
- the backlight side polarizing plate has a polarizer and two polarizing plate protective films disposed on both surfaces of the polarizer, and the polarization on the outer side of the backlight side polarizing plate.
- the selective reflection member is not used as the plate protective film
- at least the selective reflection member side (opposite side of the liquid crystal cell) of the two polarizing plate protective films may be a cellulose acylate film. preferable.
- Cellulose resin is an ester of cellulose and fatty acid.
- Specific examples of the cellulose ester resin include triacetyl cellulose, diacetyl cellulose, tripropyl cellulose, dipropyl cellulose, and the like. Among these, triacetyl cellulose is particularly preferable.
- Many products of triacetylcellulose are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available products of triacetylcellulose include trade names “UV-50”, “UV-80”, “SH-80”, “TD-80U”, “TD-TAC”, “UZ” manufactured by Fuji Film Co., Ltd. -TAC "and” KC series "manufactured by Konica.
- cyclic polyolefin resin examples are preferably norbornene resins.
- the cyclic olefin-based resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin.
- cyclic olefin ring-opening (co) polymers examples include cyclic olefin addition polymers, cyclic olefins and ⁇ -olefins such as ethylene and propylene (typically random copolymers), And the graft polymer which modified these with unsaturated carboxylic acid or its derivative (s), and those hydrides, etc. are mentioned.
- Specific examples of the cyclic olefin include norbornene monomers.
- cyclic polyolefin resins Various products are commercially available as cyclic polyolefin resins. Specific examples include the product names “ZEONEX” and “ZEONOR” manufactured by ZEON CORPORATION, the product name “ARTON” manufactured by JSR Corporation, the product name “TOPAS” manufactured by TICONA, and the product rules manufactured by Mitsui Chemicals, Inc. “APEL” may be mentioned.
- any appropriate (meth) acrylic resin can be adopted as long as the effects of the present invention are not impaired.
- poly (meth) acrylate such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester- (Meth) acrylic acid copolymers, (meth) methyl acrylate-styrene copolymers (MS resin, etc.), polymers having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, And methyl methacrylate- (meth) acrylate norbornyl copolymer).
- Preferable examples include C1-6 alkyl poly (meth) acrylates such as poly (meth) acrylate methyl. More preferred is a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by mass, preferably 70 to 100% by mass).
- the (meth) acrylic resin examples include, for example, (Meth) acrylic resin having a ring structure in the molecule described in Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and JP-A-2004-70296. And a high Tg (meth) acrylic resin system obtained by intramolecular crosslinking or intramolecular cyclization reaction.
- (Meth) acrylic resin having a lactone ring structure can also be used as the (meth) acrylic resin. It is because it has high mechanical strength by high heat resistance, high transparency, and biaxial stretching.
- the thickness of the protective film can be appropriately set, but is generally about 1 to 500 ⁇ m from the viewpoints of workability such as strength and handling, and thin layer properties. 1 to 300 ⁇ m is particularly preferable, and 5 to 200 ⁇ m is more preferable. The protective film is particularly suitable when the thickness is 5 to 150 ⁇ m.
- Re ( ⁇ ) and Rth ( ⁇ ) represent in-plane retardation at wavelength ⁇ and retardation in the thickness direction, respectively.
- Re ( ⁇ ) is measured with KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments Co., Ltd.) by making light having a wavelength of ⁇ nm incident in the normal direction of the film.
- the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like.
- Rth ( ⁇ ) is calculated by the following method.
- Rth ( ⁇ ) is the above-mentioned Re ( ⁇ ) with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotary axis) (if there is no slow axis, film A total of 6 points of light having a wavelength ⁇ nm are incident in 10 degree steps from the normal direction to 50 ° on one side with respect to the normal direction of the film (arbitrary direction in the plane).
- KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed value of the average refractive index, and the input film thickness value.
- the value is calculated by KOBRA 21ADH or WR after changing its sign to negative.
- the retardation value is measured from two inclined directions with the slow axis as the tilt axis (rotation axis) (if there is no slow axis, the arbitrary direction in the film plane is the rotation axis).
- Rth can also be calculated from the following formula (A) and formula (B) based on the value, the assumed value of the average refractive index, and the input film thickness value.
- Re ( ⁇ ) represents a retardation value in a direction inclined by an angle ⁇ from the normal direction.
- nx represents the refractive index in the slow axis direction in the plane
- ny represents the refractive index in the direction orthogonal to nx in the plane
- nz is the direction orthogonal to nx and ny.
- d is the film thickness.
- Rth ( ⁇ ) is calculated by the following method.
- Rth ( ⁇ ) is ⁇ 50 ° with respect to the normal direction of the film, using Re ( ⁇ ) described above as the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotary axis).
- Re ( ⁇ ) described above as the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotary axis).
- 11 points of light having a wavelength of ⁇ nm are incident in 10 ° steps from 1 ° to + 50 °, and the measured retardation value, average refractive index assumption and input film thickness value are used as the basis.
- KOBRA 21ADH or WR Calculated by KOBRA 21ADH or WR.
- the values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. If the average refractive index is not known, it can be measured with an Abbe refractometer.
- the average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59).
- KOBRA 21ADH or WR calculates nx, ny, and nz.
- Nz (nx ⁇ nz) / (nx ⁇ ny) is further calculated from the calculated nx, ny, and nz.
- visible light means 380 nm to 780 nm.
- a measurement wavelength is 550 nm.
- the angle for example, an angle such as “90 °”
- the relationship for example, “orthogonal”, “parallel”, “crossing at 45 °”, etc.
- the range of allowable error is included. For example, it means that the angle is within the range of strict angle ⁇ 10 °, and the error from the strict angle is preferably 5 ° or less, and more preferably 3 ° or less.
- the “slow axis” of a retardation film or the like means a direction in which the refractive index is maximized.
- numerical values, numerical ranges, and qualitative expressions for example, “equivalent”, “equal”, etc.) indicating optical characteristics of each member such as a retardation region, a retardation film, and a liquid crystal layer are used.
- “front” means a normal direction with respect to the display surface
- “front contrast (CR)” is calculated from white luminance and black luminance measured in the normal direction of the display surface.
- the “viewing angle contrast (CR)” is a white measured in an oblique direction inclined from the normal direction of the display surface (for example, a direction defined by a polar angle direction of 60 degrees with respect to the display surface). The contrast calculated from the luminance and the black luminance is assumed.
- an adhesive, a pressure-sensitive adhesive, or the like can be appropriately employed depending on the polarizer and the protective film.
- the adhesive and the adhesion treatment method are not particularly limited.
- the adhesive layer made of such an adhesive can be formed as an aqueous solution coating / drying layer, etc.
- a crosslinking agent In preparing the aqueous solution, a crosslinking agent, other additives, and a catalyst such as an acid are also blended as necessary. be able to.
- a polyvinyl alcohol polymer film is used as the polarizer, it is preferable from the viewpoint of adhesiveness to use an adhesive containing a polyvinyl alcohol resin.
- an adhesive containing a polyvinyl alcohol-based resin having an acetoacetyl group is more preferable from the viewpoint of improving durability.
- the above-mentioned polyvinyl alcohol resin is not particularly limited, but preferably has an average degree of polymerization of about 100 to 3000 and an average degree of saponification of about 85 to 100 mol% from the viewpoint of adhesiveness.
- the concentration of the aqueous adhesive solution is not particularly limited, but is preferably 0.1 to 15% by mass, and more preferably 0.5 to 10% by mass.
- the thickness of the adhesive layer is preferably about 30 to 1000 nm, more preferably 50 to 300 nm in terms of the thickness after drying. If this thickness is too thin, the adhesive strength is insufficient, and if it is too thick, the probability of appearance problems increases.
- thermosetting resins such as (meth) acrylic, urethane-based, acrylurethane-based, epoxy-based, silicone-based, or ultraviolet curable resins can be used.
- the liquid crystal cell of a general structure includes, for example, a pair of substrates arranged opposite to each other and a liquid crystal layer sandwiched between the pair of substrates, and may include a color filter layer, if necessary.
- the driving mode of the liquid crystal cell is not particularly limited, and is twisted nematic (TN), super twisted nematic (STN), vertical alignment (VA), in-plane switching (IPS), optically compensated bend cell (OCB). Various modes such as can be used.
- the liquid crystal cell used in the liquid crystal display device of the present invention is preferably a VA mode, an OCB mode, an IPS mode, or a TN mode, but is not limited thereto.
- a TN mode liquid crystal cell rod-like liquid crystal molecules are substantially horizontally aligned when no voltage is applied, and are twisted and aligned at 60 to 120 °.
- the TN mode liquid crystal cell is most frequently used as a color TFT liquid crystal display device, and is described in many documents.
- a VA mode liquid crystal cell rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied.
- the VA mode liquid crystal cell includes: (1) a narrowly defined VA mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. Hei 2-). 176625) (2) Liquid crystal cell (SID97, Digest of tech. Papers (Preliminary Proceed) 28 (1997) 845 in which the VA mode is converted into a multi-domain (MVA mode) for widening the viewing angle.
- VA mode liquid crystal cell includes: (1) a narrowly defined VA mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. Hei 2-). 176625) (2) Liquid crystal cell (SID97, Digest of tech. Papers (Preliminary Proceed) 28 (1997) 845 in which the VA mode is converted into a multi-domain (MVA mode) for widening the
- a liquid crystal cell in which rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied, and twisted multi-domain alignment is applied when a voltage is applied (Preliminary collections 58-59 (1998)) and (4) SURVIVAL mode liquid crystal cells (announced at LCD International 98).
- any of a PVA (Patterned Vertical Alignment) type, a photo-alignment type (Optical Alignment), and a PSA (Polymer-Stained Alignment) may be used. Details of these modes are described in JP-A-2006-215326 and JP-T 2008-538819.
- JP-A-10-54982, JP-A-11-202323, and JP-A-9-292522 are methods for reducing leakage light during black display in an oblique direction and improving the viewing angle using an optical compensation sheet. No. 11-133408, No. 11-305217, No. 10-307291, and the like.
- a liquid crystal display device has a liquid crystal cell in which a liquid crystal layer is sandwiched between substrates provided with electrodes on at least one opposite side, and the liquid crystal cell is arranged between two polarizing plates.
- the liquid crystal display device includes a liquid crystal cell in which liquid crystal is sealed between upper and lower substrates, and displays an image by changing the alignment state of the liquid crystal by applying a voltage. Furthermore, it has an accompanying functional layer such as a polarizing plate protective film, an optical compensation member that performs optical compensation, and an adhesive layer as necessary.
- the liquid crystal display device of the present invention may include other members.
- the liquid crystal display device of the present invention may include other members.
- a surface layer such as an undercoat layer may be disposed.
- the pixel in the present invention can be formed using various known RGB pixel forming methods.
- a desired black matrix and R, G, and B pixel patterns can be formed on a glass substrate by using a photomask and a photoresist, and colored inks for R, G, and B pixels can be used.
- Ink jet printing apparatus is used in a black matrix having a predetermined width and an area (a concave portion surrounded by convex portions) divided by a black matrix wider than the width of the black matrix described above every n.
- the ink composition is discharged until a desired concentration is obtained, and a color filter composed of R, G, and B patterns can be produced.
- a color filter composed of R, G, and B patterns
- each pixel and the black matrix may be completely cured by baking or the like.
- Preferred characteristics of the color filter are described in Japanese Patent Application Laid-Open No. 2008-083611 and the like, and the content of this publication is incorporated in the present invention.
- it is preferable that one wavelength is 590 nm to 610 nm and the other wavelength is 470 nm to 500 nm in the color filter showing green.
- one of the wavelengths having a transmittance that is half of the above-described maximum transmittance in the green color filter is 590 nm to 600 nm.
- the maximum transmittance of the color filter showing green is 80% or more.
- the wavelength having the maximum transmittance is preferably 530 nm or more and 560 nm or less.
- the light source of the light source unit described above preferably has an emission peak wavelength in the wavelength region of 600 nm to 700 nm of 620 nm to 650 nm.
- the light source included in the light source unit has a light emission peak in a wavelength region of 600 nm to 700 nm.
- the transmittance at the wavelength of the light emission peak is 10% or less of the maximum transmittance. It is preferable that The above-described color filter exhibiting red color preferably has a transmittance at 580 nm or more and 590 nm or less of 10% or less of the maximum transmittance.
- color filter pigment blue is C.I. I. Pigment Blue 15: 6 and complementary pigment C.I. I. Pigment Violet 23 is used. In red, C.I. I. Pigment Red 254 as a complementary color C.I. I. Pigment Yellow 139 is used.
- green pigment C.I. I. Pigment Green 36 (copper bromide phthalocyanine green), C.I. I. Pigment Green 7 (copper chloride phthalocyanine green) as a complementary color pigment C.I. I. Pigment Yellow 150 or C.I. I. Pigment Yellow 138 or the like is used. It can be controlled by adjusting the composition of these pigments.
- the half-value wavelength on the long wavelength side can be set in the range of 590 nm to 600 nm.
- pigments are generally used.
- color filters using dyes may be used as long as they are pigments that can control spectroscopy and ensure process stability and reliability.
- Black matrix In the liquid crystal display device of the present invention, a black matrix is disposed between each pixel.
- the material for forming the black stripe include a material using a sputtered film of a metal such as chromium, and a light-shielding photosensitive composition in which a photosensitive resin and a black colorant are combined.
- the black colorant include carbon black, titanium carbon, iron oxide, titanium oxide, graphite, and the like. Among these, carbon black is preferable.
- the liquid crystal display device of the present invention preferably further includes a TFT substrate having a thin layer transistor (hereinafter also referred to as TFT).
- TFT thin layer transistor
- the thin film transistor described above preferably includes an oxide semiconductor layer having a carrier concentration of less than 1 ⁇ 10 14 / cm 3 .
- a preferred embodiment of the above-described thin layer transistor is described in Japanese Patent Application Laid-Open No. 2011-141522, and the contents of this publication are incorporated in the present invention.
- Example 1 ⁇ Preparation of polarizing plate 1> A commercially available cellulose acylate film “TD60” (manufactured by FUJIFILM Corporation) was used as a front side polarizing plate protective film for the backlight side polarizing plate. As the rear side polarizing plate protective film of the backlight side polarizing plate, a cellulose acylate film “TD60” (manufactured by FUJIFILM Corporation) was used. A polarizer is manufactured in the same manner as [0219] to [0220] of JP-A-2006-293275, and the two polarizing plate protective films are bonded to both sides of the polarizer to manufacture the polarizing plate 1. did.
- UV narrow band UV reflective dielectric multilayer film 2-A is disclosed in IDW / AD '12, p. The total thickness is changed to 5 ⁇ m with reference to 985 to 988 (2012), and the peak of the maximum reflectance in the wavelength band corresponding to UV light is manufactured to have a reflection center wavelength of 365 nm and a half-value width of 30 nm. did.
- the UV-reflecting dielectric multilayer film 1-A in the narrow band is manufactured by cutting the UV reflecting dielectric multilayer film 2-A by 90 ° into the same size as the UV reflecting dielectric multilayer film 2-A. . On the polarizing plate 1, the UV reflecting dielectric multilayer film 2-A and the UV reflecting dielectric multilayer film 1-A were bonded in this order using an acrylic adhesive having a refractive index of 1.47.
- the quantum rod 1 When the non-polarized UV light of the UV light emitting diode is incident, the quantum rod 1 emits blue light with a center wavelength of 450 nm and a half width of 40 nm, and green light with a center wavelength of 540 nm and a half width of 40 nm.
- Quantum rod 2 and red with a center wavelength of 645 nm and a half-value width of 30 nm
- a quantum rod 3 that emits fluorescent light of colored light was formed.
- the shape of the quantum rods 1, 2, and 3 was a rectangular parallelepiped shape, and the average length of the long axes of the quantum rods was 30 nm. In addition, the average of the length of the long axis of a quantum rod was confirmed with the transmission electron microscope.
- the quantum rod sheet 1 in which the quantum rods were dispersed was produced by the following method.
- a sheet of isophthalic acid copolymerized polyethylene terephthalate (hereinafter referred to as “amorphous PET”) in which 6 mol% of isophthalic acid was copolymerized was prepared.
- the glass transition temperature of amorphous PET is 75 ° C.
- a laminate composed of an amorphous PET substrate and a quantum rod alignment layer was prepared as follows.
- the quantum rod alignment layer includes manufactured quantum rods 1, 2, and 3 using polyvinyl alcohol (hereinafter referred to as “PVA”) as a matrix.
- PVA polyvinyl alcohol
- the glass transition temperature of PVA is 80 ° C.
- a quantum rod-containing PVA aqueous solution was prepared by dissolving 4 to 5% concentration of PVA powder having a polymerization degree of 1000 or more and a saponification degree of 99% or more, and 1% each of the quantum rods 1, 2, and 3 prepared above in water. .
- An amorphous PET substrate having a thickness of 200 ⁇ m was prepared.
- a quantum rod-containing PVA aqueous solution is applied to the above-mentioned 200 ⁇ m-thick amorphous PET substrate, dried at a temperature of 50 to 60 ° C., and a 25 ⁇ m-thick quantum rod-containing PVA layer is formed on the amorphous PET substrate.
- This laminate of amorphous PET and quantum rod-containing PVA is called a quantum rod sheet 1.
- the quantum rod sheet 1 was stretched uniaxially at a free end so as to be stretched by a stretching apparatus provided in an oven set at a stretching temperature environment of 130 ° C. so that the stretching ratio was 3 times.
- the quantum rod-containing PVA layer in the stretched laminate was changed to a 15 ⁇ m-thick quantum rod-containing PVA layer in which the PVA molecules were aligned and the quantum rods were aligned accordingly.
- This will be referred to as a quantum rod alignment sheet 1.
- the long axis orientation state of the quantum rod was confirmed with a transmission electron microscope.
- the mass of the quantum rod per unit area was 0.005 g / m 2 .
- a commercially available liquid crystal display device (manufactured by Panasonic, trade name TH-L42D2) was disassembled, and the backlight-side polarizing plate was provided with the UV reflective dielectric multilayer films 2-A and 1-A prepared above on the rear side.
- the polarizing plate 1 is changed to the quantum rod alignment sheet 1 manufactured above between the UV reflective dielectric multilayer film 1-A and the backlight unit.
- the liquid crystal display device of Example 1 was manufactured by changing the backlight unit to the following UV narrow-band backlight unit.
- the UV narrow-band backlight unit used was a surface light source including a UV light-emitting diode (Nichia UV-LED: NC4U133A, main wavelength 365 nm, half-width 9 nm, hereinafter also referred to as UV light source) and a light guide plate as light sources.
- a reflection member that reflects light emitted from the light source and reflected by the optical sheet member is provided at the rear of the light source.
- Example 2 ⁇ Formation of selective reflection member> IDW / AD '12, p.
- the dielectric multilayer film 2-B was manufactured in the same manner as in the production of the dielectric multilayer film 2-A used in Example 1, except that the total thickness was changed to 3 ⁇ m with reference to 985 to 988 (2012). Formed.
- a dielectric multilayer film 1-B was formed in the same manner as in the production of the dielectric multilayer film 1-A used in Example 1. On the polarizing plate 1, a UV reflective dielectric multilayer film 2-B and a UV reflective dielectric multilayer film 1-B were bonded in this order in the same manner as in Example 1.
- Example 1 instead of the polarizing plate 1 in which the UV reflecting dielectric multilayer films 2-A and 1-A are arranged on the rear side, the UV reflecting dielectric multilayer films 2-B and 1-B formed as described above are used.
- a liquid crystal display device of Example 2 was manufactured in the same manner as Example 1 except that the polarizing plate 1 disposed on the rear side was used.
- Example 3 ⁇ Formation of selective reflection member> (Formation of a light reflecting layer with a fixed cholesteric liquid crystal phase)
- Fujifilm research report no. 50 (2005) pp. With reference to 60-63, the addition amount of the chiral agent used was changed, and one light reflecting layer formed by fixing the cholesteric liquid crystal phase was formed by coating.
- the light reflection layer formed by fixing the obtained cholesteric liquid crystal phase was designated as UV reflection CLC1 (left circular polarization reflection). Similar to the formation of UV reflective CLC1 (left circularly polarized reflection) except that the type of chiral agent used was changed to that capable of forming a left spiral cholesteric liquid crystal structure on top of UV reflective CLC1 (left circularly polarized reflective).
- the light reflection layer formed by fixing the obtained cholesteric liquid crystal phase was designated as UV reflection CLC2 (right circular polarization reflection).
- the reflection center wavelengths of the maximum reflectance peaks of UV reflection CLC1 (left circular polarization reflection) and UV reflection CLC2 (right circular polarization reflection) are both 365 nm, the half width is 40 nm, the film thickness is 3 ⁇ m, All ⁇ n was 0.12, and the average refractive index was 1.57.
- the reflection center wavelength was 365 nm
- the half width 100 nm
- the film thickness was 3 ⁇ m.
- UV reflection CLC2 right circular polarization reflection
- UV reflection CLC1 left circular polarization reflection
- UV reflection CLC2 right circular polarization reflection
- UV The reflection CLC 1 was peeled off and transferred onto the surface of the polarizing plate 1.
- Example 1 ⁇ Manufacture of liquid crystal display devices>
- the liquid crystal display device of Example 3 was manufactured in the same manner as Example 1 except that the following points were changed.
- UV reflective CLC2 right circularly polarized reflective
- a selective reflection member having UV reflection CLC1 was used.
- Example 4 In Example 3, from a laminate having UV reflection CLC2 (right circular polarization reflection) and UV reflection CLC1 (left circular polarization reflection) on a support, UV reflection CLC2 (right circular polarization reflection) and UV reflection CLC1 (left circle). A liquid crystal display device of Example 4 was produced in the same manner as in Example 3 except that (polarized reflection) was transferred onto the liquid crystal cell instead of being transferred onto the polarizing plate 1.
- Example 1 In the production of the liquid crystal display device of Example 3, a comparison was made in the same manner as in Example 3 except that the polarizing plate 1 produced above was used instead of the laminate of the polarizing plate 1, the UV reflective CLC2, and the UV reflective CLC1. The liquid crystal display device of Example 1 was manufactured.
- a dielectric multilayer film (trade name DBEF, manufactured by 3M Co., Ltd., described as conventional DBEF in Table 1 below) was bonded between the backlight side polarizing plate and the backlight unit.
- a liquid crystal display device of Comparative Example 2 was manufactured by separating and arranging without providing the agent layer.
- the dielectric multilayer film (trade name DBEF) had a reflectance of a peak that was almost constant from 300 to 450 to 550 to 630 nm in the ultraviolet to blue to green to red region and flat with respect to the wavelength.
- the front luminance (white luminance) of the liquid crystal display device was measured by the method described in [0180] of JP-A-2009-93166. The results are shown in Table 1 below. Incidentally, the front luminance is practical liquid crystal display device, must be at 200 cd / m 2 or more, preferably 210 cd / m 2 or more, more preferably 220 cd / m 2 or more.
- the color gamut (NTSC ratio) of the liquid crystal display device was measured by the method described in JP-A-2012-3073 [0066]. The results are shown in Table 1 below.
- the color gamut (NTSC ratio) of the liquid crystal display device is preferably 80% or more, more preferably 90% or more, and particularly preferably 100%.
- the external light reflectance of the liquid crystal display device was measured with a colorimeter (manufactured by Minolta, CM-2022) according to the method described in Japanese Patent Application Laid-Open No. 2009-186605. The results are shown in Table 1 below. Note that the external light reflectance of the liquid crystal display device is preferably 10% or less, more preferably 6% or less, and particularly preferably 5% or less.
- the front contrast of the liquid crystal display device was measured by the method described in [0180] of JP-A-2009-93166. The results are shown in Table 1 below.
- the front contrast of the liquid crystal display device is preferably 300 or more, more preferably 1000 or more, and particularly preferably 1100 or more.
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Abstract
Description
近年の液晶表示装置において、LCD性能改善として省電力化、高精細化、色再現性向上のための開発が進んでおり、特にタブレットPCやスマートフォンなどの小型サイズで顕著に省電力化、高精細化、色再現性向上が求められているのが現状だが、大型サイズにおいても現行のTV規格(FHD、NTSC(National Television System Committee)比72%≒EBU(European Broadcasting Union)比100%)の次世代ハイビジョン(4K2K、EBU比100%以上)の開発が進められている。そのため、液晶表示装置の省電力化、高精細化、色再現性向上がますます求められている。
このような光学シート部材として、バックライトとバックライト側偏光板の間に特定の光学シート部材(DBEF(Dual Brightness Enhancement Film、二重輝度向上フィルム)など)を設ける事で、光リサイクルによりBLの光利用効率を向上させ、バックライトを省電力化しつつ、その輝度を向上させる技術が知られている(特許文献1参照)。同様に特許文献2には、λ/4板とコレステリック液晶相を積層した構成の偏光板が記載されている。コレステリック液晶相のピッチの異なる3層以上のコレステリック液晶相を固定してなる層で広帯域化することにより、光リサイクルでBLの光利用効率を向上させることができる。
しかし、このような光学シート部材は部材構成が複雑であり、市場に普及するためには、より部材の機能統合を進めた部材点数低減での低コスト化が必須となっている。
また、特許文献4には、紫色LEDまたは青色LEDが照射する光の経路上に、量子ドットからなる蛍光体を含む蛍光体層を配置することで、カラーフィルターでのエネルギー損失を少なくし、液晶ディスプレイのエネルギー効率を高くする方法が提案されている。
省電力化に必要なBL光利用率改善を含めて正面輝度を向上することができる、新規な部材構成の液晶表示装置を提供することが本発明の解決しようとする課題である。また、より部材の機能統合を進めた部材点数低減による低コスト化も本発明の目的である。
すなわち、上記課題は、以下の構成の本発明によって解決される。
バックライトユニットが、300nm以上430nm未満の波長帯域に発光中心波長を有する無偏光の光を発光する光源を備え;
選択反射部材が、この選択反射部材に入射する前述の無偏光の光の60~100%を反射し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過し;
光変換部材が、この光変換部材に入射する前述の無偏光の光により、
430~480nmの波長帯域に発光中心波長を有し、かつ表示側偏光子の吸収軸と平行な振動方向の直線偏光である青色光、
500~600nmの波長帯域に発光中心波長を有し、かつ表示側偏光子の吸収軸と平行な振動方向の直線偏光である緑色光、および、
600~650nmの波長帯域に発光中心波長を有し、かつ表示側偏光子の吸収軸と平行な振動方向の直線偏光である赤色光、
を発光する配向した蛍光材料を含む;
液晶表示装置。
[2] [1]に記載の液晶表示装置は、前述の無偏光の光が第1の偏光状態の光および第2の偏光状態の光からなり;
選択反射部材が、バックライト側から順に第1の選択反射領域と第2の選択反射領域とを含み、
第1の選択反射領域が、第1の選択反射領域に入射する前述の無偏光の光のうち前述の第1の偏光状態の光を反射し、前述の第2の偏光状態の光をその偏光状態を維持したまま透過し、430nmを超え650nm以下の波長帯域の光を透過し、
第2の選択反射領域が、第1の選択反射領域を通過して第2の選択反射領域に入射する前述の第2の偏光状態の光を反射し、430nmを超え650nm以下の波長帯域の光を透過することが好ましい。
[3] [1]または[2]に記載の液晶表示装置は、選択反射部材が、第1の誘電体多層膜および第2の誘電体多層膜をこの順に有し、
第1の誘電体多層膜が300~430nmの波長帯域に反射中心波長を有し、反射中心波長において第1の方向の直線偏光を反射し、この第1の方向に直交する第2の方向の直線偏光を透過し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過し;
第2の誘電体多層膜が300~430nmの波長帯域に反射中心波長を有し、反射中心波長において前述の第2の方向の直線偏光を反射し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過することが好ましい。
[4] [1]または[2]に記載の液晶表示装置は、選択反射部材が、第1のコレステリック液晶相を固定してなる光反射層および第2のコレステリック液晶相を固定してなる光反射層をこの順に有し、
第1のコレステリック液晶相を固定してなる光反射層が300~430nmの波長帯域に反射中心波長を有し、反射中心波長において右円偏光および左円偏光のうち一方を反射し、他の一方を透過し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過し;
第2のコレステリック液晶相を固定してなる光反射層が300~430nmの波長帯域に反射中心波長を有し、反射中心波長において第1のコレステリック液晶相を固定してなる光反射層とは異なる方向の円偏光を反射し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過することが好ましい。
[5] [1]~[4]のいずれか一つに記載の液晶表示装置は、選択反射部材と液晶セルとの間にバックライト側偏光子を有し、
バックライト側偏光子と表示側偏光子の吸収軸が直交することが好ましい。
[6] [5]に記載の液晶表示装置は、バックライト側偏光子の両表面に2枚の偏光板保護フィルムを有し、
2枚の偏光板保護フィルムのうち少なくとも選択反射部材側の偏光板保護フィルムがセルロースアシレートフィルムであることが好ましい。
[7] [1]~[6]のいずれか一つに記載の液晶表示装置は、蛍光材料が少なくとも量子ドットを含むことが好ましい。
[8] [7]に記載の液晶表示装置は、量子ドットが、楕円体形状または直方体形状の量子ロッドであることが好ましい。
[9] [8]に記載の液晶表示装置は、量子ロッドの長軸方向が、表示側偏光子の吸収軸と平行な方向に配向されてなることが好ましい。
[10] [1]~[9]のいずれか一つに記載の液晶表示装置は、光変換部材が、蛍光材料を分散させた後に延伸されてなる配向蛍光シートであることが好ましい。
[11] [1]~[10]のいずれか一つに記載の液晶表示装置は、光変換部材が発光する前述の青色光と前述の緑色光と前述の赤色光が、いずれも半値幅が100nm以下である発光強度のピークを有することが好ましい。
[12] [1]~[11]のいずれか一つに記載の液晶表示装置は、バックライトユニット全体が面光源であることが好ましい。
[13] [1]~[12]のいずれか一つに記載の液晶表示装置は、バックライトユニットが発光する前述の無偏光の光の発光中心波長が300~380nmの波長帯域にあることが好ましい。
[14] [1]~[13]のいずれか一つに記載の液晶表示装置は、バックライトユニットが発光する前述の無偏光の光が、半値幅が30nm以下である発光強度のピークを有することが好ましい。
[15] [1]~[14]のいずれか一つに記載の液晶表示装置は、バックライトユニットが、300~430nmの波長帯域の一部または全部の光を反射できる反射部材を備えることが好ましい。
以下に記載する構成要件の説明は、本発明の代表的な実施態様に基づいてなされることがあるが、本発明はそのような実施態様に限定されるものではない。なお、本明細書において「~」を用いて表される数値範囲は、「~」の前後に記載される数値を下限値および上限値として含む範囲を意味する。
本明細書中、ピークの「半値幅」とは、ピーク高さ1/2でのピークの幅のことを言う。無偏光とは、偏光特性を持たない光である。
本発明の液晶表示装置は、バックライトユニット、光変換部材、選択反射部材、液晶セルおよび表示側偏光子がこの順で配置され;
バックライトユニットが、300nm以上430nm未満の波長帯域に発光中心波長を有する無偏光の光を発光する光源を備え;
選択反射部材が、この選択反射部材に入射する前述の無偏光の光の60~100%を反射し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過し;
光変換部材が、この光変換部材に入射する前述の無偏光の光により、
430~480nmの波長帯域に発光中心波長を有し、かつ表示側偏光子の吸収軸と平行な振動方向の直線偏光である青色光、
500~600nmの波長帯域に発光中心波長を有し、かつ表示側偏光子の吸収軸と平行な振動方向の直線偏光である緑色光、および、
600~650nmの波長帯域に発光中心波長を有し、かつ表示側偏光子の吸収軸と平行な振動方向の直線偏光である赤色光、
を発光する配向した蛍光材料を含む;ことを特徴とする。
このような構成により、本発明の液晶表示装置は正面輝度が改善され、部材点数の削減による部材厚さの薄膜化もできる。紫外光~青色の一部の領域のバックライトの光の大部分を反射でき、かつ、可視光を透過することができる選択反射部材と、紫外光~短波長の青色の光が入射すると青色と緑色と赤色の直線偏光を発光する配向した蛍光材料(有機、無機、量子ドットなど)を含む光変換部材とを組み合わせて用いることにより、バックライトの光の液晶セルよりもバックライト側での吸収を抑制して光利用率を高めることができる。
また、表示側偏光子の透過軸が、上述の青色光、上述の緑色光および上述の赤色光の振動方向と平行であるため、上述の青色光、上述の緑色光および上述の赤色光はいずれもバックライト側偏光板がなくとも偏光状態が揃って液晶セルに入射することができる。
図1~図5に、本発明の液晶表示装置の概略図を示した。
図1に示した本発明の液晶表示装置51は、バックライトユニット31、光変換部材16、選択反射部材5、液晶セル42および表示側偏光板44を含む。
本発明の液晶表示装置は、図1や図2に示すように後述のバックライト側偏光子3や、後述のバックライト側偏光板1を含まない構成としてもよい。その場合、図1に示すように液晶セル42と選択反射部材5が直接接していたり、または不図示の接着剤層を介して積層していたりしてもよく、図2に示すように液晶セル42と分離して(空気層を介して)選択反射部材5を配置してもよい。
選択反射部材5の具体的な構成としては、図1~図5に示した第1の選択反射領域5aおよび第2の選択反射領域5bをバックライト側からこの順に有する構成が好ましい。第1の選択反射領域5aとしては、誘電体多層膜やコレステリック液晶相を固定してなる光反射層を用いることができる。第2の選択反射領域5bとしては、第1の選択反射領域5aに用いた誘電体多層膜とは反射できる直線偏光の方向が直交する別の誘電体多層膜や、第1の選択反射領域5aに用いたコレステリック液晶相を固定してなる光反射層とは反射できる円偏光の方向が逆のコレステリック液晶相を固定してなる光反射層を用いることができる。但し、選択反射部材5は、図1~図5に示した構成に限定されるものではない。
バックライトユニット31に進んだ選択反射部材で反射された光33、すなわち300nm以上430nm未満の波長帯域である第1の方向の直線偏光および第2の方向の直線偏光は、バックライトユニット31を構成する任意の部材、例えば導光板31Bの界面や図4や図5に示した任意に設けられる反射部材31C、によって反射または散乱されて、300nm以上430nm未満の波長帯域の再帰反射された光37として、光変換部材16または選択反射部材5に向かう。
一方、第1の選択反射領域5aである第1の誘電体多層膜は、430nmを超え650nm以下の波長帯域の少なくとも一部の光、具体的には後述の光変換部材が発光する直線偏光の青色光34、緑色光35および赤色光36の一部または全部を透過するため、第1の選択反射領域5aである第1の誘電体多層膜を通過した光変換部材が発光する直線偏光の青色光34、緑色光35および赤色光36は、第2の選択反射領域5bに進む。第2の選択反射領域5bである第2の誘電体多層膜も430nmを超え650nm以下の波長帯域の少なくとも一部の光、具体的には後述の光変換部材が発光する直線偏光の青色光34、緑色光35および赤色光36の一部または全部も透過するため、第2の選択反射領域5bである第2の誘電体多層膜に入射した光変換部材が発光した直線偏光の青色光34、緑色光35および赤色光36は、第2の選択反射領域5bも通過して、液晶セル42または任意に設けられたバックライト側偏光子1に向かう。
バックライトユニット31に進んだ選択反射部材で反射された光33、すなわち300nm以上430nm未満の波長帯域である右円偏光および左円偏光は、バックライトユニット31を構成する任意の部材、例えば導光板31Bの界面や図4や図5に示した任意に設けられる反射部材31C、によって反射または散乱されて、300nm以上430nm未満の波長帯域の再帰反射された光37として、光変換部材16または選択反射部材5に向かう。
一方、第1の選択反射領域5aである第1のコレステリック液晶相を固定してなる光反射層は、あわせて430nmを超え650nm以下の波長帯域の少なくとも一部の光、具体的には後述の光変換部材が発光する直線偏光の青色光34、緑色光35および赤色光36の一部または全部も透過するため、第1の選択反射領域5aである第1のコレステリック液晶相を固定してなる光反射層を通過した光変換部材が発光する直線偏光の青色光34、緑色光35および赤色光36は、第2の選択反射領域5bに進む。第2の選択反射領域5bである第2のコレステリック液晶相を固定してなる光反射層も430nmを超え650nm以下の波長帯域の少なくとも一部の光、具体的には後述の光変換部材が発光する直線偏光の青色光34、緑色光35および赤色光36の一部または全部も透過するため、第2の選択反射領域5bである第2のコレステリック液晶相を固定してなる光反射層に入射した光変換部材が発光した直線偏光の青色光34、緑色光35および赤色光36は、第2の選択反射領域5bも通過して、液晶セル42または任意に設けられたバックライト側偏光子1に向かう。
すなわち、上述の青色光34と、上述の緑色光35と、上述の赤色光36の振動方向は同じ方向となる。
光変換部材16に入射する無偏光の光としては、バックライトユニットが発光した300nm以上430nm未満の波長帯域に発光中心波長を有する無偏光の光32と;300nm以上430nm未満の波長帯域に発光中心波長を有する、選択反射部材で反射された光33と;300nm以上430nm未満の波長帯域に発光中心波長を有する、バックライトユニット31を構成する任意の部材によって再帰反射された光37を挙げることができる。
バックライト側偏光子3の少なくともどちらか一方の面に偏光板保護フィルムを積層配置したものをバックライト側偏光板1と呼び、バックライト側偏光板の構成としては特に制限はなく公知の構成を採用することができ、例えば、偏光板保護フィルム(インナー側)2、偏光子3および偏光板保護フィルム(アウター側)4の積層体の構成とすることができる。また、例えば、インナー側には偏光板保護フィルムを設けず、偏光子の上に直接粘着剤や、塗膜を設けるインナーレス構成とすることができる。また更に、アウター側の偏光板保護フィルムとして、またはアウター側の偏光板保護フィルム4の代わりに、前述の選択反射部材5を用いる事ができる。すなわち、選択反射部材5が、バックライト側偏光板中に含まれるアウター側の偏光板保護フィルム4を兼用することができる。
表示側偏光子46を含む表示側偏光板44としては特に制限はなく公知の構成を採用することができ、例えば、図1~図5に示したように偏光板保護フィルム(アウター側)45、表示側偏光子46および偏光板保護フィルム(インナー側)47の積層体の構成とすることができる。
本発明の液晶表示装置は、バックライトユニットが300nm以上430nm未満の波長帯域に発光中心波長を有する無偏光の光を発光する光源を備える。
バックライトとしては、導光板や反射板などを構成部材とするエッジライト方式であっても、直下型方式であっても構わないが、本発明の液晶表示装置は、バックライトユニット全体が面光源であることが好ましい。本発明の液晶表示装置は、バックライトユニットが光源またはエッジライト方式の場合は導光板の後部に、光源から発光されて選択反射部材で反射された光の反射(繰り返しの再帰反射)をする反射部材を備えることが好ましい。反射部材は、液晶表示装置の明るさを向上させることができればよく、光源から発光されて選択反射部材で反射された光の偏光状態がその方向および偏光状態をランダム化され再循環されるものであってもよい。このような反射部材としては特に制限は無く、公知のものを用いることができ、特許3416302号、特許3363565号、特許4091978号、特許3448626号などに記載されており、これらの公報の内容は本発明に組み込まれる。
本発明の液晶表示装置は、バックライトユニットの光源は、前述の300nm以上430nm未満の波長帯域に発光中心波長を有する光を発光するUV発光ダイオートや青色発光ダイオードを有することが好ましく、UV発光ダイオートを有することがより好ましい。
本発明の液晶表示装置は、バックライトユニットが発光する無偏光の光が、半値幅が100nm以下である発光強度のピークを有することが好ましく、半値幅が80nm以下である発光強度のピークを有することがより好ましく、半値幅が70nm以下である発光強度のピークを有することが特に好ましく、半値幅が30nm以下である発光強度のピークを有することがより特に好ましく、半値幅が10nm以下である発光強度のピークを有することがさらにより特に好ましい。
本発明の液晶表示装置は、バックライトユニットが発光する無偏光の光の発光中心波長と、選択反射部材の反射中心波長が一致することが好ましい。具体的には、バックライトユニットが発光する無偏光の光の発光中心波長と、選択反射部材に含まれる第1の選択反射領域と第2の選択反射領域の反射中心波長が一致することが好ましい。より具体的には、バックライトユニットが発光する無偏光の光の発光中心波長と、第1の選択反射領域として用いられる第1の誘電体多層膜の反射中心波長と、第2の選択反射領域として用いられる第2の誘電体多層膜の反射中心波長とが一致することが好ましい。または、バックライトユニットが発光する無偏光の光の発光中心波長と、第1の選択反射領域として用いられる第1のコレステリック液晶相を固定してなる光反射層の反射中心波長と、第2の選択反射領域として用いられる第2のコレステリック液晶相を固定してなる光反射層の反射中心波長とが一致することが好ましい。本明細書中、2つの波長が「一致」するとは、2つの波長が完全に波長が一致する場合に限定されるものではなく、2つの波長が光学的に許容し得る程度のズレを有している場合も含む。バックライトユニットが発光する無偏光の光の発光中心波長と、選択反射部材の反射中心波長との差は、50nm以内であることが好ましく、20nm以内であることがより好ましく、10nm以内であることが特に好ましい。また、本明細書中、発光中心波長とは、発光強度のスペクトルのピークが最大値をとる波長のことをいう。また、本明細書中、反射中心波長とは、反射率のスペクトルのピークが最大値をとる波長のことをいう。
本発明の液晶表示装置は光変換部材を含み、この光変換部材に入射する前述の無偏光の光により、430~480nmの波長帯域に発光中心波長を有し、かつ表示側偏光子の吸収軸と平行な振動方向の直線偏光である青色光;500~600nmの波長帯域に発光中心波長を有し、かつ表示側偏光子の吸収軸と平行な振動方向の直線偏光である緑色光;および、600~650nmの波長帯域に発光中心波長を有し、かつ表示側偏光子の吸収軸と平行な振動方向の直線偏光である赤色光、を発光する配向した蛍光材料を含む。
本発明の液晶表示装置は光変換部材が直線偏光を出射するために、光変換部材が配向した蛍光材料を含むことを特徴とし、すなわち光変換部材が配向されてなる。光変換部材が発光する光の偏光状態は、例えばAxometrics社のAxoscanで偏光測定することで計測することができる。
本発明の液晶表示装置は、光変換部材が発光する上述の青色光と上述の緑色光と上述の赤色光が、いずれも半値幅が100nm以下である発光強度のピークを有することが好ましく、半値幅が80nm以下である発光強度のピークを有することがより好ましく、半値幅が70nm以下である発光強度のピークを有することが特に好ましい。
また、有機の蛍光材料も用いることができ、例えば、特開2001-174636号公報、特開2001-174809号公報などに記載蛍光材料を用いることができる。
有機または無機の蛍光材料、例えば染料や顔料、を有する光変換部材としては、これらの蛍光材料が配向したシート、これらの蛍光材料を分散させた後に延伸されてなる熱可塑性フィルム、または、これらの蛍光材料を分散させて配向させた接着層であることが好ましい。
このような楕円体形状または直方体形状の量子ロッドとしては特に制限は無く、米国特許7303628号、論文(Peng, X. G.; Manna, L.; Yang, W. D.; Wickham, j.; Scher, E.; Kadavanich, A.; Alivisatos, A. P. Nature 2000, 404, 59-61)及び論文(Manna, L.; Scher, E. C.; Alivisatos, A. P. j. Am. Chem. Soc. 2000, 122, 12700-12706)などに記載の楕円体形状または直方体形状の量子ロッドを用いることができ、これらの文献の内容は本発明に組み込まれる。量子ロッドの形状の確認方法としては特に制限は無く、透過型電子顕微鏡を用いて確認することができる。
本発明の液晶表示装置は、量子ロッドの長軸方向がバックライト側偏光子の透過軸と平行な方向に配向されてなることが、光変換部材への入射光の直線偏光の振動方向によらず一定の所望の振動方向(表示側偏光子の吸収軸と平行な方向、かつ、好ましくはバックライト側偏光子の透過軸と平行な方向)の直線偏光の光を発光でき、好ましい。量子ロッドの長軸方向の確認方法としては特に制限は無く、透過型電子顕微鏡を用いて確認することができる。
量子ロッドの長軸方向を表示側偏光子の吸収軸と平行な方向またはバックライト側偏光子の透過軸と平行な方向に配向させる方法としては特に制限はないが、例えば以下の方法を挙げることができる。
前述の蛍光材料を有する光変換部材が、量子ロッド材料を分散させた後に延伸されてなる熱可塑性フィルムを用いることができ、このような熱可塑性フィルムとしては特に制限は無く、公知のものを用いることができるが、例えば特開2001-174636号公報、特開2001-174809号公報などに記載されており、これらの文献の内容は本発明に組み込まれる。
前述の蛍光材料が、量子ロッドである場合、前述の光変換部材に以下の含有量で含まれることが好ましい。
単位面積あたりの量子ロッドの質量が0.000001~2g/m2の範囲にあることが好ましく、0.000005~0.02g/m2の範囲にあることがより好ましく、0.00001~0.01g/m2の範囲にあることがもっとも好ましい。
本発明の液晶表示装置は、前述の選択反射部材が、この選択反射部材に入射する無偏光の光の60~100%を反射し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過する。すなわち、バックライトユニットから発光された300nm以上430nm未満の波長帯域に発光中心波長を有する無偏光の光や、バックライトユニットで再帰反射された光に対して選択的に反射機能を奏し、430nmを超え650nm以下の波長帯域の少なくとも一部の光に対して反射機能を奏さないことが好ましい。
前述の選択反射部材は、この選択反射部材に入射する300nm以上430nm未満の波長帯域の無偏光の光の80~100%を反射することが好ましく、90~100%を反射することがより好ましく、95~100%を反射することが特に好ましく、99~100%を反射することがより特に好ましい。
選択反射部材は、300~430nmの波長帯域に反射中心波長を有し、反射中心波長が300~380nmの波長帯域にあることが好ましく、350~380nmの波長帯域にあることがより好ましい。
300~430nmの波長帯域に反射中心波長を有する反射率のピークは、半値幅が100nm以下である反射率のピークであることが好ましく、半値幅が80nm以下である反射率のピークであることがより好ましく、半値幅が70nm以下である反射率のピークであることが特に好ましく、半値幅が20nm以下である反射率のピークであることがより特に好ましく、半値幅が10nm以下である反射率のピークであることがさらにより特に好ましい。
具体的には、前述の選択反射部材が、光変換部材から発光された430~480nmの波長帯域に発光中心波長を有し、かつ表示側偏光子の吸収軸と平行な振動方向の直線偏光である青色光の少なくとも一部を透過することが好ましく、上述の青色光の発光中心波長の光を透過することがより好ましく、上述の青色光の発光ピークの全部を透過することが特に好ましい。前述の選択反射部材は、430~480nmの波長帯域において最大の反射率のピークが20%以下であることが好ましく、430~480nmの波長帯域において最大の反射率のピークが10%以下であることがより好ましく、430~480nmの波長帯域において最大の反射率のピークが5%以下であることが特に好ましい。
また、前述の選択反射部材が、光変換部材から発光された500~600nmの波長帯域に発光中心波長を有し、かつ表示側偏光子の吸収軸と平行な振動方向の直線偏光である緑色光の少なくとも一部を透過することが好ましく、上述の緑色光の発光中心波長の光を透過することがより好ましく、上述の緑色光の発光ピークの全部を透過することが特に好ましい。前述の選択反射部材は、500~600nmの波長帯域において最大の反射率のピークが20%以下であることが好ましく、500~600nmの波長帯域において最大の反射率のピークが10%以下であることがより好ましく、500~600nmの波長帯域において最大の反射率のピークが5%以下であることが特に好ましい。
前述の選択反射部材が、光変換部材から発光された600~650nmの波長帯域に発光中心波長を有し、かつ表示側偏光子の吸収軸と平行な振動方向の直線偏光である赤色光の少なくとも一部を透過することが好ましく、上述の赤色光の発光中心波長の光を透過することがより好ましく、上述の赤色光の発光ピークの全部を透過することが特に好ましい。前述の選択反射部材は、600~650nmの波長帯域において最大の反射率のピークが20%以下であることが好ましく、600~650nmの波長帯域において最大の反射率のピークが10%以下であることがより好ましく、600~650nmの波長帯域において最大の反射率のピークが5%以下であることが特に好ましい。
前述の選択反射部材は、この選択反射部材に入射した430nmを超え650nm以下の波長帯域の光の偏光状態とこの選択反射部材から出射される430nmを超え650nm以下の波長帯域の光の偏光状態が実質的に同じとなることが好ましく、具体的にはこの選択反射部材に入射した430nmを超え650nm以下の波長帯域の直線偏光の振動方向とこの選択反射部材から出射される430nmを超え650nm以下の波長帯域の直線偏光の振動方向が平行であることが好ましい。ただし、前述の選択反射部材に入射した光と出射される光の偏光状態が実質的に同じとなれば、前述の選択反射部材を通過している途中でこの選択反射部材に入射した430nmを超え650nm以下の波長帯域の光の偏光状態が変化してもよく、例えば前述の選択反射部材の内部で遅相軸が直交する2枚のλ/4板を通過させてもよい。
本発明の液晶表示装置の態様(i)では、前述の選択反射部材が、第1の誘電体多層膜および第2の誘電体多層膜をこの順に有し、第1の誘電体多層膜が300~430nmの波長帯域に反射中心波長を有し、反射中心波長において第1の方向の直線偏光を反射し、この第1の方向に直交する第2の方向の直線偏光を透過し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過し;第2の誘電体多層膜が300~430nmの波長帯域に反射中心波長を有し、反射中心波長において前述の第2の方向の直線偏光を反射し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過することが好ましい。
この態様(i)に用いられる誘電体多層膜は、この誘電体多層膜に入射した300~430nmの波長帯域の無偏光の光に対して、直線偏光を反射または透過(出射)する。300~430nmの波長帯域のうち、すべての波長帯域においてほぼ一定で波長に対しフラットな1つの反射率のピークを有する場合もこの態様(i)に含まれる。
なお、図1~図5では第1の選択反射領域5aまたは第2の選択反射領域5bは図面作成の便宜上、単層として描かれているが、本発明に用いられる誘電体多層膜はこのような具体例によって限定されるものではなく、誘電体多層膜の積層数は目的とする反射率や反射中心波長を達成するために適宜変更することができる。
300~430nmの波長帯域に反射中心波長を有し、反射中心波長において第1の方向の直線偏光を反射し、この第1の方向に直交する第2の方向の直線偏光を透過する第1の誘電体多層膜と、300~430nmの波長帯域に反射中心波長を有し、反射中心波長において前述の第2の方向の直線偏光を反射する第2の誘電体多層膜の組み合わせとしては特に制限は無い。例えば、第1の誘電体多層膜と同じ誘電体多層膜を、第1の誘電体多層膜とは90°回転させて積層することで、第2の誘電体多層膜として用いることができる。
300~430nmの波長帯域に反射中心波長を有し、反射中心波長において第1の方向の直線偏光を反射し、この第1の方向に直交する第2の方向の直線偏光を透過する第1の誘電体多層膜と、300~430nmの波長帯域に反射中心波長を有し、反射中心波長において前述の第2の方向の直線偏光を反射する第2の誘電体多層膜の積層方法としては特に制限は無い。例えば、第1の誘電体多層膜と同じ誘電体多層膜を、第1の誘電体多層膜とは90°回転させて積層したものを第2の誘電体多層膜とし、両者の間を後述の接着剤や粘着材で貼り合わせることで本発明の光反射部材とすることができる。
本発明の液晶表示装置の態様(ii)では、前述の選択反射部材が、第1のコレステリック液晶相を固定してなる光反射層および第2のコレステリック液晶相を固定してなる光反射層をこの順に有し、第1のコレステリック液晶相を固定してなる光反射層が300~430nmの波長帯域に反射中心波長を有し、反射中心波長において右円偏光および左円偏光のうち一方を反射し、他の一方を透過し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過し;第2のコレステリック液晶相を固定してなる光反射層が300~430nmの波長帯域に反射中心波長を有し、反射中心波長において第1のコレステリック液晶相を固定してなる光反射層とは異なる方向の円偏光を反射し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過することが好ましい。
この態様(ii)に用いられるコレステリック液晶相を固定してなる光反射層は、このコレステリック液晶相を固定してなる光反射層に入射した300~430nmの波長帯域の無偏光の光に対して、右円偏光および左円偏光の一方を反射または透過(出射)する。300~430nmの波長帯域のうち、一部の波長帯域(例えば360~400nm)においてほぼ一定で波長に対し最大値がフラットかつ立ち上がりが急峻な1つの反射率のピークを有し、その他の波長(例えば300~360nmや400~430nm)は反射率0%であるような反射スペクトルであるコレステリック液晶相を固定してなる光反射層もこの態様(ii)に含まれる。
300~430nmの波長帯域に反射中心波長を有し、反射中心波長において第1の方向の直線偏光を反射し、この第1の方向に直交する第2の方向の直線偏光を透過する第1のコレステリック液晶相を固定してなる光反射層と、300~430nmの波長帯域に反射中心波長を有し、反射中心波長において前述の第2の方向の直線偏光を反射する第2のコレステリック液晶相を固定してなる光反射層の積層方法としては特に制限は無い。例えば、右旋回性のキラル剤を用いた第1のコレステリック液晶相を固定してなる光反射層の上に、左旋回性のキラル剤を用いた第2のコレステリック液晶相を固定してなる光反射層を塗布し、必要に応じて乾燥、硬化することで本発明の光反射部材とすることができる。
以下、特開平8-271731号公報に記載の方法について説明する。
本発明の液晶表示装置は、選択反射部材と、液晶セルまたはバックライト側偏光子とが、直接、接着層を介して、または、偏光板保護フィルムを介して隣接して配置されたことが好ましい。
また、選択反射部材は、第1の選択反射領域および第2の選択反射領域がこの順で、直接接触して、または、接着層を介して積層したことが好ましい。
部材統合により、部材膜厚の薄層化や部材間隙の空気層での界面反射ロス低減、液晶表示装置製造時や製造後に発生する可能性がある部材間への異物混入による表示不良をなくすことができる。
粘着剤層としては、例えば、動的粘弾性測定装置で測定した貯蔵弾性率G’と損失弾性率G”との比(tanδ=G”/G’)が0.001~1.5である物質のことを表し、いわゆる、粘着剤やクリープしやすい物質等が含まれる。本発明に用いることのできる粘着剤としては、例えば、アクリル系粘着剤や、ポリビニルアルコール系接着剤が挙げられるが、これに限定されない。
このようなフィラーの粒子径(JIS B9921)は、0.1~20.0μm、好ましくは1.0~10.0μmの範囲が望ましい。特に、0.5~10μmの範囲が好ましい。
フィラーの屈折率(JIS K-7142によるB法)は、粘着剤の屈折率に対して0.05~0.5の差があることが好ましく、より好ましくは0.05~0.3が良い。
拡散粘着層におけるフィラーの含有量は、1.0~40.0質量%、特に、3.0~20質量%であることが望ましい。
次に、バックライト側偏光板および表示側偏光板について説明する。
本発明の液晶表示装置が有する偏光板は、偏光子およびそのどちらか一方の面に配置された偏光板保護フィルムを含むことが好ましく、偏光子およびその両側に配置された二枚の偏光板保護フィルム(以下、保護フィルムとも言う)からなることがより好ましいが、バックライト側偏光板のアウター側の偏光板保護フィルムとして前述の選択反射部材を用いてもよく、バックライト側偏光板のインナー側の偏光板保護フィルムは使用しなくてもよい。前述の選択反射部材をバックライト側偏光板のアウター側の偏光板保護フィルムとして用いず、選択反射部材を偏光板保護フィルムとは独立した部材として用いる場合、本発明ではより薄膜化するために保護フィルムをより薄く(60μm以下、好ましくは40μm以下、より好ましくは25μm以下)することが好ましい。アクリル樹脂などの保護レジンを塗布、乾燥、硬化したハードコート(20μm以下、好ましくは10μm以下、より好ましくは5μm以下)を使用することがより好ましい。
保護層を設けない偏光子を用いることがより薄手化の実現にはさらに好ましい。
本発明においては、二枚の偏光板保護フィルムの内、液晶セル側に配置されるインナー側の偏光板保護フィルムとして、VA、IPS、TN、OCBモードの液晶表示装置の場合位相差フィルムが用いられることがより好ましいが、IPSモードの場合は位相差が略ない光学補償フィルムを使用することが好ましく、インナー側の偏光板保護フィルムを使用しないことが、より薄手化の実現には好ましい。
前述の偏光子としては、ポリマーフィルムにヨウ素が吸着配向されたものを用いることが好ましい。前述のポリマーフィルムとしては、特に限定されず各種のものを使用できる。例えば、ポリビニルアルコール系フィルム、ポリエチレンテレフタレート系フィルム、エチレン・酢酸ビニル共重合体系フィルムや、これらの部分ケン化フィルム、セルロース系フィルム等の親水性高分子フィルムに、ポリビニルアルコールの脱水処理物やポリ塩化ビニルの脱塩酸処理物等ポリエン系配向フィルム等が挙げられる。これらの中でも、偏光子としてのヨウ素による染色性に優れたポリビニルアルコール系フィルムを用いることが好ましい。
前述の保護フィルムのうち、液晶セルと反対側に配置される保護フィルムとしては、透明性、機械的強度、熱安定性、水分遮断性、等方性等に優れる熱可塑性樹脂が用いられる。この様な熱可塑性樹脂の具体例としては、トリアセチルセルロース等のセルロース樹脂、ポリエステル樹脂、ポリエーテルスルホン樹脂、ポリスルホン樹脂、ポリカーボネート樹脂、ポリアミド樹脂、ポリイミド樹脂、ポリオレフィン樹脂、(メタ)アクリル樹脂、環状ポリオレフィン樹脂(ノルボルネン系樹脂)、ポリアリレート樹脂、ポリスチレン樹脂、ポリビニルアルコール樹脂、及びこれらの混合物が挙げられる。
特に本発明の液晶表示装置は、バックライト側偏光板が、偏光子とこの偏光子の両表面に配置された2枚の偏光板保護フィルムを有し、バックライト側偏光板のアウター側の偏光板保護フィルムとして前述の選択反射部材を用いない場合は、2枚の偏光板保護フィルムのうち少なくとも選択反射部材側(液晶セルと反対側)の偏光板保護フィルムがセルロースアシレートフィルムであることが好ましい。
Rth(λ)は、前述のRe(λ)を、面内の遅相軸(KOBRA 21ADH、又はWRにより判断される)を傾斜軸(回転軸)として(遅相軸がない場合には、フィルム面内の任意の方向を回転軸とする)のフィルム法線方向に対して法線方向から片側50°まで10度ステップで各々その傾斜した方向から波長λnmの光を入射させて全部で6点測定し、その測定されたレターデーション値と平均屈折率の仮定値及び入力された膜厚値を基にKOBRA 21ADH又はWRが算出する。上記において、法線方向から面内の遅相軸を回転軸として、ある傾斜角度にレターデーションの値がゼロとなる方向をもつフィルムの場合には、その傾斜角度より大きい傾斜角度でのレターデーション値はその符号を負に変更した後、KOBRA 21ADH、又はWRが算出する。なお、遅相軸を傾斜軸(回転軸)として(遅相軸がない場合には、フィルム面内の任意の方向を回転軸とする)、任意の傾斜した2方向からレターデーション値を測定し、その値と平均屈折率の仮定値、及び入力された膜厚値を基に、以下の式(A)、及び式(B)よりRthを算出することもできる。
Rth=((nx+ny)/2-nz)×d・・・・・・・・・・式(B)
また、本明細書において、角度(例えば「90°」等の角度)、及びその関係(例えば「直交」、「平行」、及び「45°で交差」等)については、本発明が属する技術分野において許容される誤差の範囲を含むものとする。例えば、厳密な角度±10°未満の範囲内であることなどを意味し、厳密な角度との誤差は、5°以下であることが好ましく、3°以下であることがより好ましい。
また、本明細書において、位相差領域、位相差フィルム、及び液晶層等の各部材の光学特性を示す数値、数値範囲、及び定性的な表現(例えば、「同等」、「等しい」等の表現)については、液晶表示装置やそれに用いられる部材について一般的に許容される誤差を含む数値、数値範囲及び性質を示していると解釈されるものとする。
また、本明細書で「正面」とは、表示面に対する法線方向を意味し、「正面コントラスト(CR)」は、表示面の法線方向において測定される白輝度及び黒輝度から算出されるコントラストをいい、「視野角コントラスト(CR)」は、表示面の法線方向から傾斜した斜め方向(例えば、表示面に対して、極角方向60度で定義される方向)において測定される白輝度及び黒輝度から算出されるコントラストをいうものとする。
前述の偏光子と保護フィルムの貼り合わせには、偏光子ならびに保護フィルムに応じて、接着剤や粘着剤等を適宜採用することができる。この接着剤および接着処理方法としては特に限定されるものではないが、例えば、ビニルポリマーからなる接着剤、あるいは、少なくともホウ酸やホウ砂、グルタルアルデヒドやメラミン、シュウ酸などのビニルアルコール系ポリマーの水溶性架橋剤からなる接着剤などを介して行うことができる。このような接着剤からなる接着層は、水溶液の塗布乾燥層などとして形成しうるが、その水溶液の調製に際しては、必要に応じて、架橋剤や他の添加剤、酸等の触媒も配合することができる。特に偏光子としてポリビニルアルコール系のポリマーフィルムを用いる場合には、ポリビニルアルコール系樹脂を含有する接着剤を用いることが、接着性の点から好ましい。さらには、アセトアセチル基を有するポリビニルアルコール系樹脂を含む接着剤が耐久性を向上させる点からより好ましい。
液晶セルの構成については特に制限はなく、一般的な構成の液晶セルを採用することができる。液晶セルは、例えば、対向配置された一対の基板と、この一対の基板間に挟持された液晶層とを含み、必要に応じて、カラーフィルター層などを含んでいてもよい。液晶セルの駆動モードについても特に制限はなく、ツイステットネマチック(TN)、スーパーツイステットネマチック(STN)、バーティカルアライメント(VA)、インプレインスイッチング(IPS)、オプティカリーコンペンセイテットベンドセル(OCB)等の種々のモードを利用することができる。
TNモードの液晶セルでは、電圧無印加時に棒状液晶性分子が実質的に水平配向し、更に60~120゜にねじれ配向している。TNモードの液晶セルは、カラーTFT液晶表示装置として最も多く利用されており、多数の文献に記載がある。
VAモードの液晶セルでは、電圧無印加時に棒状液晶性分子が実質的に垂直に配向している。VAモードの液晶セルには、(1)棒状液晶性分子を電圧無印加時に実質的に垂直に配向させ、電圧印加時に実質的に水平に配向させる狭義のVAモードの液晶セル(特開平2-176625号公報記載)に加えて、(2)視野角拡大のため、VAモードをマルチドメイン化した(MVAモードの)液晶セル(SID97、Digest of tech.Papers(予稿集)28(1997)845記載)、(3)棒状液晶性分子を電圧無印加時に実質的に垂直配向させ、電圧印加時にねじれマルチドメイン配向させるモード(n-ASMモード)の液晶セル(日本液晶討論会の予稿集58~59(1998)記載)及び(4)SURVIVALモードの液晶セル(LCDインターナショナル98で発表)が含まれる。また、PVA(Patterned Vertical Alignment)型、光配向型(Optical Alignment)、及びPSA(Polymer-Sustained Alignment)のいずれであってもよい。これらのモードの詳細については、特開2006-215326号公報、及び特表2008-538819号公報に詳細な記載がある。
IPSモードの液晶セルは、棒状液晶分子が基板に対して実質的に平行に配向しており、基板面に平行な電界が印加することで液晶分子が平面的に応答する。IPSモードは電界無印加状態で黒表示となり、上下一対の偏光板の吸収軸は直交している。光学補償シートを用いて、斜め方向での黒表示時の漏れ光を低減させ、視野角を改良する方法が、特開平10-54982号公報、特開平11-202323号公報、特開平9-292522号公報、特開平11-133408号公報、特開平11-305217号公報、特開平10-307291号公報などに開示されている。
また、本発明の液晶表示装置は、他の部材を含んでいてもよい。例えば、カラーフィルター基板、薄層トランジスタ基板、レンズフィルム、拡散シート、ハードコート層、反射防止層、低反射層、アンチグレア層等とともに(又はそれに替えて)、前方散乱層、プライマー層、帯電防止層、下塗り層等の表面層が配置されていてもよい。
本発明における画素は、光源が500nm以下の可視のBを用いている場合、RGB画素形成方法としては、公知の種々の方法を用いて形成させることができる。例えば、ガラス基板上にフォトマスク、およびフォトレジストを用いて所望のブラックマトリックス、およびR、G、Bの画素パターンを形成することもできるし、また、R、G、Bの画素用着色インクを用いて、所定の幅のブラックマトリクス、及びn個置きに前述のブラックマトリクスの幅よりも広いブラックマトリックスで区分された領域内(凸部で囲まれた凹部)に、インクジェット方式の印刷装置を用いて所望の濃度になるまでインク組成物の吐出を行い、R、G、Bのパターンからなるカラーフィルターを作製することもできる。画像着色後は、ベーク等することで各画素及びブラックマトリックスを完全に硬化させてもよい。
カラーフィルターの好ましい特性は特開2008-083611号公報などに記載されており、この公報の内容は本発明に組み込まれる。
例えば、緑色を示すカラーフィルターにおける最大透過率の半分の透過率となる波長は、一方が590nm以上610nm以下であり、他方が470nm以上500nm以下であることが好ましい。また、緑色を示すカラーフィルターにおいて前述の最大透過率の半分の透過率となる波長は、一方が590nm以上600nm以下であることが好ましい。さらに緑色を示すカラーフィルターにおける最大透過率は80%以上であることが好ましい。緑色を示すカラーフィルターにおいて最大透過率となる波長は530nm以上560nm以下であることが好ましい。
前述の光源ユニットが有する光源は、600nm以上700nm以下の波長領域における発光ピークの波長が620nm以上650nm以下であることが好ましい。前述の光源ユニットが有する光源は、600nm以上700nm以下の波長領域に発光ピークを有し、前述の緑色を示すカラーフィルターにおいて、前述の発光ピークの波長における透過率は、最大透過率の10%以下であることが好ましい。
前述の赤色を示すカラーフィルターは、580nm以上590nm以下における透過率が最大透過率の10%以下であることが好ましい。
本発明の液晶表示装置は、各画素の間にブラックマトリックスが配置される。ブラックストライプを形成する材料としては、クロム等の金属のスパッタ膜を用いたもの、感光性樹脂と黒色着色剤等を組み合わせた遮光性感光性組成物などが挙げられる。黒色着色剤の具体例としては、カーボンブラック、チタンカーボン、酸化鉄、酸化チタン、黒鉛などが挙げられ、中でも、カーボンブラックが好ましい。
本発明の液晶表示装置は、さらに薄層トランジスタ(以下、TFTとも言う)を有するTFT基板を有することが好ましい。
前述の薄層トランジスタが、キャリア濃度が1×1014/cm3未満である酸化物半導体層を有することが好ましい。前述の薄層トランジスタの好ましい態様については特開2011-141522号公報に記載されており、この公報の内容は本発明に組み込まれる。
<偏光板1の準備>
バックライト側偏光板のフロント側偏光板保護フィルムとして市販のセルロースアシレート系フィルム「TD60」(富士フイルム社製)を用いた。
バックライト側偏光板のリア側偏光板保護フィルムとして、セルロースアシレート系フィルム「TD60」(富士フイルム社製)を用いた。
特開2006-293275号公報の[0219]~[0220]と同様にして、偏光子を製造し、上記2枚の偏光板保護フィルムを偏光子の両面にそれぞれ貼り合わせて、偏光板1を製造した。
(誘電体多層膜の形成)
UV狭帯域のUV反射誘電体多層膜2-Aは、IDW/AD ’12、p.985~988(2012)を参考にトータル厚さを5μmとなるように変更し、UV光に対応する波長帯域における最大反射率のピークの反射中心波長は365nm、半値幅は30nmとなるように製造した。
UV狭帯域のUV反射誘電体多層膜1-Aは、UV反射誘電体多層膜2-Aを90°回転させたものを、UV反射誘電体多層膜2-Aと同じサイズに切り出して製造した。
偏光板1の上に、UV反射誘電体多層膜2-AおよびUV反射誘電体多層膜1-Aをこの順にそれぞれ屈折率1.47のアクリル系接着剤を用いて貼り合わせた。
UV反射誘電体多層膜2-AおよびUV反射誘電体多層膜1-Aを有する選択反射部材に入射した無偏光のUV光の反射率として、波長365nmにおける反射率を、分光光度計“V-550”(日本分光(株)製)で測定した。その結果を下記表1に記載した。
光変換部材として、米国特許7303628、論文(Peng, X. G.; Manna, L.; Yang, W. D.; Wickham, j.; Scher, E.; Kadavanich, A.; Alivisatos, A. P. Nature 2000, 404, 59-61)及び論文(Manna, L.; Scher, E. C.; Alivisatos, A. P. j. Am. Chem. Soc. 2000, 122, 12700-12706)を参考に、UV発光ダイオードの無偏光のUV光が入射したときに、中心波長450nm、半値幅40nmの青色光の蛍光発光をする量子ロッド1と、中心波長540nm、半値幅40nmの緑色光の蛍光発光をする量子ロッド2と、中心波長645nm、半値幅30nmの赤色光の蛍光発光をする量子ロッド3を形成した。量子ロッド1、2、3の形状は直方体形状であり、量子ロッドの長軸の長さの平均は30nmであった。なお、量子ロッドの長軸の長さの平均は、透過型電子顕微鏡で確認した。次に、量子ロッドを分散した量子ロッドシート1を以下の方法で作製した。
基材として、イソフタル酸を6mol%共重合させたイソフタル酸共重合ポリエチレンテレフタレート(以下、「非晶性PET」という)のシートを作製した。非晶性PETのガラス転移温度は75℃である。非晶性PET基材と量子ロッド配向層からなる積層体を以下のように作製した。ここで量子ロッド配向層はポリビニルアルコール(以下、「PVA」という)をマトリクスとして、作製した量子ロッド1、2、3を含む。ちなみにPVAのガラス転移温度は80℃である。
重合度1000以上、ケン化度99%以上のPVA粉末4~5%濃度、及び上記で作製した量子ロッド1、2、3それぞれ1%濃度を水に溶解した、量子ロッド含有PVA水溶液を準備した。また厚み200μmの非晶性PET基材を準備した。次に、上記した厚み200μmの非晶性PET基材に量子ロッド含有PVA水溶液を塗布し、50~60℃の温度で乾燥し、非晶性PET基材上に厚み25μmの量子ロッド含有PVA層を製膜した。この非晶性PETと量子ロッド含有PVAの積層体を量子ロッドシート1と呼ぶ。
市販の液晶表示装置(パナソニック社製、商品名TH-L42D2)を分解し、バックライト側偏光板を上記にて製造したUV反射誘電体多層膜2-Aおよび1-Aをリア側に配した偏光板1に変更し、UV反射誘電体多層膜1-Aとバックライトユニットの間に上記にて製造した量子ロッド配向シート1を蛍光材料の配向方向が表示側偏光板(市販品)の吸収軸と平行になるように配置し、バックライトユニットを以下のUV狭帯域バックライトユニットに変更し、実施例1の液晶表示装置を製造した。
用いたUV狭帯域バックライトユニットは、光源としてUV発光ダイオード(日亜UV-LED:NC4U133A、主波長365nm、半値幅9nm、以下UV光源とも言う)と導光板を備える面光源であった。また、光源の後部に光源から発光されて前述の光学シート部材で反射された光の反射をする反射部材を備える。
<選択反射部材の形成>
IDW/AD ’12、p.985~988(2012)を参考にトータル厚さを3μmとなるように変更した以外は実施例1で用いた誘電体多層膜2-Aの製造と同様にして、誘電体多層膜2-Bを形成した。実施例1で用いた誘電体多層膜1-Aの製造と同様にして、誘電体多層膜1-Bを形成した。
偏光板1の上に、UV反射誘電体多層膜2-BおよびUV反射誘電体多層膜1-Bをこの順に実施例1と同様にして貼り合わせた。
実施例1において、UV反射誘電体多層膜2-Aおよび1-Aをリア側に配した偏光板1の代わりに、上記にて形成したUV反射誘電体多層膜2-Bおよび1-Bをリア側に配した偏光板1を用いた以外は実施例1と同様にして、実施例2の液晶表示装置を製造した。
<選択反射部材の形成>
(コレステリック液晶相を固定してなる光反射層の形成)
支持体の上に、富士フイルム研究報告 No.50(2005年)pp.60-63を参考に、用いたキラル剤の添加量を変更して、コレステリック液晶相を固定してなる光反射層を塗布により1層形成した。得られたコレステリック液晶相を固定してなる光反射層をUV反射CLC1(左円偏光反射)とした。
UV反射CLC1(左円偏光反射)の上に、用いたキラル剤の種類を左螺旋のコレステリック液晶構造を形成できるものに変更した以外はUV反射CLC1(左円偏光反射)の形成と同様にして、コレステリック液晶相を固定してなる光反射層を塗布により1層形成した。得られたコレステリック液晶相を固定してなる光反射層をUV反射CLC2(右円偏光反射)とした。
UV反射CLC1(左円偏光反射)およびUV反射CLC2(右円偏光反射)の最大反射率のピークの反射中心波長はいずれも365nm、半値幅はいずれも40nm、膜厚はいずれも3μm、液晶のΔnはいずれも0.12、平均屈折率はいずれも1.57であった。また、Δn=0.17の液晶を用いた場合、反射中心波長は365nm、半値幅は100nm、膜厚は3μmを実現できた。
支持体上にUV反射CLC2(右円偏光反射)およびUV反射CLC1(左円偏光反射)を有する積層体に入射した無偏光のUV光の反射率を、分光光度計“V-550”(日本分光(株)製)で測定した。その結果を下記表1に記載した。
実施例1において、以下の点を変更した以外は実施例1と同様にして、実施例3の液晶表示装置を製造した。
偏光板1の上にUV反射誘電体多層膜2-AおよびUV反射誘電体多層膜1-Aを有する選択反射部材の代わりに、偏光板1の上にUV反射CLC2(右円偏光反射)およびUV反射CLC1を有する選択反射部材を用いた。
実施例3において、支持体上にUV反射CLC2(右円偏光反射)およびUV反射CLC1(左円偏光反射)を有する積層体から、UV反射CLC2(右円偏光反射)およびUV反射CLC1(左円偏光反射)を偏光板1の上に転写する代わりに、液晶セルの上に転写した以外は実施例3と同様にして、実施例4の液晶表示装置を製造した。
実施例3の液晶表示装置の製造において、偏光板1とUV反射CLC2とUV反射CLC1の積層体の代わりに、上記に製造した偏光板1を用いた以外は実施例3と同様にして、比較例1の液晶表示装置を製造した。
実施例3の液晶表示装置の製造において、誘電体多層膜(商品名DBEF、スリーエム・カンパニー社製、下記表1には従来DBEFと記載)をバックライト側偏光板とバックライトユニットの間に接着剤層を設けずに分離して配置し、比較例2の液晶表示装置を製造した。
誘電体多層膜(商品名DBEF)は、紫外~青~緑~赤領域の300~450~550~630nmまでほぼ一定で波長に対しフラットなピークの反射率であった。
各実施例および比較例の液晶表示装置を以下の基準にしたがって評価した。
液晶表示装置の正面輝度(白色輝度)を、特開2009-93166号公報の〔0180〕に記載の方法で測定した。その結果を下記表1に記載した。
なお、液晶表示装置の正面輝度は実用上、200cd/m2以上であることが必要であり、210cd/m2以上であることが好ましく、220cd/m2以上であることがより好ましい。
液晶表示装置の色再現域(NTSC比)を、特開2012-3073号公報の〔0066〕に記載の方法で測定した。その結果を下記表1に記載した。
なお、液晶表示装置の色再現域(NTSC比)は80%以上であることが好ましく、90%以上であることがより好ましく、100%であることが特に好ましい。
液晶表示装置の外光反射率を、特開2009-186605号公報に記載の方法に従い、測色計(ミノルタ社製、CM-2022)で測定した。その結果を下記表1に記載した。
なお、液晶表示装置の外光反射率は10%以下であることが好ましく、6%以下であることがより好ましく、5%以下であることが特に好ましい。
液晶表示装置の正面コントラストを、特開2009-93166号公報の〔0180〕に記載の方法で測定した。
その結果を下記表1に記載した。
なお、液晶表示装置の正面コントラストは300以上であることが好ましく、1000以上であることがより好ましく、1100以上であることが特に好ましい。
一方、比較例1および2より、本発明の構成を満たす選択反射部材を用いない場合は、正面輝度が低いことがわかった。具体的には、比較例1より、選択反射部材を全く用いない場合は、正面輝度が著しく低いことがわかった。比較例2より、本発明の構成を満たす選択反射部材の代わりに、UV狭帯域の誘電体多層膜(DBEF)を1種のみ用い、反射率が本発明で規定する下限値を下回る選択反射部材を用いた場合は、正面輝度が低いことがわかった。
なお、上記表1より、本発明の液晶表示装置の好ましい態様では、色再現域、外光反射率、正面コントラストも良好となることもわかった。
なお、光変換部材が表示側偏光板の偏光子の吸収軸と平行な方向に振動方向を有する直線偏光を出射していることを本明細書中に記載の方法で確認した。
2 偏光板保護フィルム(インナー側)
3 バックライト側偏光子
4 偏光板保護フィルム(アウター側)
5 選択反射部材
5a 第1の選択反射領域
5b 第2の選択反射領域
16 光変換部材(無偏光の光から、直線偏光の青色光、直線偏光の緑色光および直線偏光の赤色光へ変換)
17B、17G、17R 配向した蛍光材料
31 バックライトユニット
31A 光源
31B 導光板
31C 反射部材
32 無偏光の光(バックライトユニットからの入射光)
33 選択反射部材で反射された光
34 青色光(光変換部材が発光した直線偏光の青色光)
35 緑色光(光変換部材が発光した直線偏光の緑色光)
36 赤色光(光変換部材が発光した直線偏光の赤色光)
37 再帰反射された光
42 液晶セル
44 表示側偏光板
45 偏光板保護フィルム(アウター側)
46 表示側偏光子
47 偏光板保護フィルム(インナー側)
51 液晶表示装置
Claims (15)
- バックライトユニット、光変換部材、選択反射部材、液晶セルおよび表示側偏光子がこの順で配置され;
前記バックライトユニットが、300nm以上430nm未満の波長帯域に発光中心波長を有する無偏光の光を発光する光源を備え;
前記選択反射部材が、前記選択反射部材に入射する前記無偏光の光の60~100%を反射し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過し;
前記光変換部材が、前記光変換部材に入射する前記無偏光の光により、
430~480nmの波長帯域に発光中心波長を有し、かつ前記表示側偏光子の吸収軸と平行な振動方向の直線偏光である青色光、
500~600nmの波長帯域に発光中心波長を有し、かつ前記表示側偏光子の吸収軸と平行な振動方向の直線偏光である緑色光、および、
600~650nmの波長帯域に発光中心波長を有し、かつ前記表示側偏光子の吸収軸と平行な振動方向の直線偏光である赤色光、
を発光する配向した蛍光材料を含む;
ことを特徴とする液晶表示装置。 - 前記無偏光の光が第1の偏光状態の光および第2の偏光状態の光からなり;
前記選択反射部材が、バックライト側から順に第1の選択反射領域と第2の選択反射領域とを含み、
前記第1の選択反射領域が、前記第1の選択反射領域に入射する前記無偏光の光のうち前記第1の偏光状態の光を反射し、前記第2の偏光状態の光をその偏光状態を維持したまま透過し、430nmを超え650nm以下の波長帯域の光を透過し、
前記第2の選択反射領域が、前記第1の選択反射領域を通過して前記第2の選択反射領域に入射する前記第2の偏光状態の光を反射し、430nmを超え650nm以下の波長帯域の光を透過する、請求項1に記載の液晶表示装置。 - 前記選択反射部材が、第1の誘電体多層膜および第2の誘電体多層膜をこの順に有し、
前記第1の誘電体多層膜が300~430nmの波長帯域に反射中心波長を有し、前記反射中心波長において第1の方向の直線偏光を反射し、前記第1の方向に直交する第2の方向の直線偏光を透過し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過し;
前記第2の誘電体多層膜が300~430nmの波長帯域に反射中心波長を有し、前記反射中心波長において前記第2の方向の直線偏光を反射し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過する、請求項1または2に記載の液晶表示装置。 - 前記選択反射部材が、第1のコレステリック液晶相を固定してなる光反射層および第2のコレステリック液晶相を固定してなる光反射層をこの順に有し、
前記第1のコレステリック液晶相を固定してなる光反射層が300~430nmの波長帯域に反射中心波長を有し、前記反射中心波長において右円偏光および左円偏光のうち一方を反射し、他の一方を透過し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過し;
前記第2のコレステリック液晶相を固定してなる光反射層が300~430nmの波長帯域に反射中心波長を有し、前記反射中心波長において前記第1のコレステリック液晶相を固定してなる光反射層とは異なる方向の円偏光を反射し、430nmを超え650nm以下の波長帯域のうち少なくとも一部の光を透過する、請求項1または2に記載の液晶表示装置。 - 前記選択反射部材と前記液晶セルとの間にバックライト側偏光子を有し、
前記バックライト側偏光子と前記表示側偏光子の吸収軸が直交する、請求項1~4のいずれか一項に記載の液晶表示装置。 - 前記バックライト側偏光子の両表面に2枚の偏光板保護フィルムを有し、
前記2枚の偏光板保護フィルムのうち少なくとも前記選択反射部材側の偏光板保護フィルムがセルロースアシレートフィルムである、請求項5に記載の液晶表示装置。 - 前記蛍光材料が少なくとも量子ドットを含む、請求項1~6のいずれか一項に記載の液晶表示装置。
- 前記量子ドットが、楕円体形状または直方体形状の量子ロッドである、請求項7に記載の液晶表示装置。
- 前記量子ロッドの長軸方向が、前記表示側偏光子の吸収軸と平行な方向に配向されてなる、請求項8に記載の液晶表示装置。
- 前記光変換部材が、前記蛍光材料を分散させた後に延伸されてなる配向蛍光シートである、請求項1~9のいずれか一項に記載の液晶表示装置。
- 前記光変換部材が発光する前記青色光と前記緑色光と前記赤色光が、いずれも半値幅が100nm以下である発光強度のピークを有する、請求項1~10のいずれか一項に記載の液晶表示装置。
- 前記バックライトユニット全体が面光源である、請求項1~11のいずれか一項に記載の液晶表示装置。
- 前記バックライトユニットが発光する前記無偏光の光の発光中心波長が300~380nmの波長帯域にある、請求項1~12のいずれか一項に記載の液晶表示装置。
- 前記バックライトユニットが発光する前記無偏光の光が、半値幅が30nm以下である発光強度のピークを有する、請求項1~13のいずれか一項に記載の液晶表示装置。
- 前記バックライトユニットが、300~430nmの波長帯域の一部または全部の光を反射できる反射部材を備える、請求項1~14のいずれか一項に記載の液晶表示装置。
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KR20160030242A (ko) | 2016-03-16 |
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