WO2010143552A1 - Transmission type liquid crystal display device - Google Patents

Transmission type liquid crystal display device Download PDF

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Publication number
WO2010143552A1
WO2010143552A1 PCT/JP2010/059216 JP2010059216W WO2010143552A1 WO 2010143552 A1 WO2010143552 A1 WO 2010143552A1 JP 2010059216 W JP2010059216 W JP 2010059216W WO 2010143552 A1 WO2010143552 A1 WO 2010143552A1
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WO
WIPO (PCT)
Prior art keywords
light
liquid crystal
diffusion layer
backlight
light diffusion
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PCT/JP2010/059216
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French (fr)
Japanese (ja)
Inventor
康博 小池
明広 多加谷
Original Assignee
独立行政法人科学技術振興機構
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Application filed by 独立行政法人科学技術振興機構 filed Critical 独立行政法人科学技術振興機構
Priority to CN201080025580.XA priority Critical patent/CN102460286B/en
Priority to KR1020127000259A priority patent/KR101375400B1/en
Priority to JP2011518441A priority patent/JP5323190B2/en
Publication of WO2010143552A1 publication Critical patent/WO2010143552A1/en

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    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00Optical elements other than lenses
    • G02B5/02Diffusing elements; Afocal elements
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033Means for improving the coupling-out of light from the light guide
    • G02B6/005Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
    • G02B6/0051Diffusing sheet or layer
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL 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
    • G02F1/00Devices 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
    • G02F1/01Devices 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 
    • G02F1/13Devices 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
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333Constructional arrangements; Manufacturing methods
    • G02F1/1335Structural association of cells with optical devices, e.g. polarisers or reflectors
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL 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
    • G02F1/00Devices 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
    • G02F1/01Devices 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 
    • G02F1/13Devices 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
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333Constructional arrangements; Manufacturing methods
    • G02F1/1335Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133504Diffusing, scattering, diffracting elements
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL 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
    • G02F1/00Devices 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
    • G02F1/01Devices 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 
    • G02F1/13Devices 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
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333Constructional arrangements; Manufacturing methods
    • G02F1/1335Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336Illuminating devices
    • G02F1/133602Direct backlight
    • G02F1/133606Direct backlight including a specially adapted diffusing, scattering or light controlling members
    • G02F1/133607Direct backlight including a specially adapted diffusing, scattering or light controlling members the light controlling member including light directing or refracting elements, e.g. prisms or lenses
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL 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
    • G02F1/00Devices 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
    • G02F1/01Devices 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 
    • G02F1/13Devices 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
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333Constructional arrangements; Manufacturing methods
    • G02F1/1335Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336Illuminating devices
    • G02F1/133615Edge-illuminating devices, i.e. illuminating from the side

Definitions

  • the present invention relates to a transmissive liquid crystal display device.
  • the transmissive liquid crystal display device is widely used as a typical flat panel display because of its excellent features such as thinness, light weight and low power consumption. In particular, it has been widely used as a TV, personal computer monitor, in-vehicle display, and mobile phone. Since the liquid crystal itself is a non-light-emitting device, it can be roughly classified into three types, a transmission type, a transflective type, and a reflective type, depending on the light irradiation method from the light source. Under circumstances where the external light is relatively weak, high image quality is realized by a transmission type system that can stably emit light of appropriate intensity from the backlight. Therefore, transmissive liquid crystal display devices are mainly used in applications that require high image quality, such as televisions and personal computer monitors.
  • the liquid crystal has a TN mode, a VA mode, an IPS mode, an OCB mode and the like in relation to the molecular arrangement. These have a viewing angle dependency due to the respective optical characteristics. Accordingly, even when the image quality such as contrast and color is designed to be good in the normal direction (front direction) of the liquid crystal panel, the image quality is deteriorated in the oblique direction.
  • a method using a viewing angle compensation film as shown in FIG. 10 and a method using a light diffusion layer as shown in FIG. 11 have been proposed.
  • the backlight having a wide angle emitted from the backlight light source 1 is transmitted through the diffuser plate 2 and then includes the viewing angle compensation film 3. Passes through the liquid crystal panel 4.
  • the viewing angle compensation film 3 is used to compensate for the phase difference between the light passing through the liquid crystal layer in the normal direction and the light passing through the liquid crystal layer.
  • FIG. 10 shows the case where two viewing angle compensation films are used, there are cases where only one or three or more are used.
  • the transparent protective film also serves as a viewing angle compensation film.
  • this viewing angle compensation film requires a high degree of birefringence control, it is generally more expensive than other optical films.
  • the phase difference between the light passing through the liquid crystal layer in the normal direction and the light passing obliquely depends on the wavelength. Therefore, the viewing angle compensation film needs to be adjusted to have birefringence wavelength dispersibility suitable for the liquid crystal layer to be used. Those having characteristics are not easily obtained.
  • the light emitted from the backlight source 1 and passing through the light guide plate 6 passes through the liquid crystal panel 4 and the light diffusing layer 5 in this order. Pass along the normal direction.
  • a light diffusion layer for example, a light diffusion layer is proposed in which transparent fine particles are spread between a polarizing plate and a glass substrate, and the gaps between the fine particles are filled with a transparent filler (see, for example, Patent Document 1). .
  • a method has been proposed in which a light diffusion film in which scatterers are dispersed in a transparent resin is used as a protective film for a polarizing plate (for example, see Patent Document 2).
  • a flat thing is described as a scatterer disperse
  • the method using the light diffusing layer is hardly used because of a problem of a decrease in contrast due to external light.
  • Patent Document 3 A method of using a viewing angle compensation film and a light diffusion layer in combination has also been proposed (see, for example, Patent Document 3).
  • a viewing angle compensation sheet mainly composed of a liquid crystalline compound and a light diffusing layer are used in combination to improve the OCB mode viewing angle, a cellulose acetate film having optical anisotropy, and a light diffusing layer. Is used together to improve the viewing angle of the VA mode.
  • the above-mentioned problem in the light diffusion layer has not been solved yet.
  • the present invention has been made in view of the above-described conventional circumstances, and an object of the present invention is to provide a transmissive liquid crystal display device that suppresses a decrease in contrast due to external light while realizing a wide viewing angle.
  • the invention according to claim 1 at least, A backlight light source;
  • Light control means for controlling the directivity of light emitted from the backlight light source;
  • a transmissive liquid crystal cell In order from the side closer to the light control means, a transmissive liquid crystal cell, a light diffusing layer containing a translucent polymer, a scatterer, and a colorant,
  • a transmissive liquid crystal display device having
  • the invention according to claim 2 2.
  • the invention according to claim 3 The transmissive liquid crystal display device according to claim 1, wherein the light diffusion layer has an internal absorbance of 0.020 or more at a main wavelength of light emitted from the backlight light source.
  • the invention according to claim 4 The transmissive liquid crystal according to any one of claims 1 to 3, wherein the light diffusion layer has an internal absorbance of 0.028 or more and 0.062 or less at a main wavelength of light emitted from the backlight light source. It is a display device.
  • the invention according to claim 5 5.
  • the invention according to claim 6 The light diffusion layer is a laminate of a scattering layer in which the light scatterers are dispersed in the light-transmitting polymer and a colored layer containing the light-transmitting polymer and the colorant.
  • the present invention it is possible to provide a transmissive liquid crystal display device that realizes a wide viewing angle and suppresses a decrease in contrast due to external light.
  • 1 is a schematic cross-sectional view illustrating an exemplary configuration of a transmissive liquid crystal display device of the present invention. 2 is an internal absorbance spectrum of Samples 11 to 14 in Example 1. 3 is an internal transmittance spectrum of Samples 11 to 14 in Example 1.
  • the transmissive liquid crystal display device of the present invention comprises at least a backlight light source, a light control means for controlling the directivity of light emitted from the backlight light source, and a transmissive type in order from the side closer to the light control means.
  • a liquid crystal cell ; and a light diffusion layer containing a light-transmitting polymer, a scatterer, and a colorant.
  • a viewing angle compensation film as shown in FIG. 10 is used in order to reduce a color shift due to a viewing angle of a liquid crystal display.
  • the viewing angle compensation film must be provided with appropriate birefringence wavelength dispersion.
  • birefringence wavelength dispersion is a characteristic inherent to the material, and it is not easy to obtain a polymer having ideal wavelength dispersion.
  • a method using the light diffusion layer shown in FIG. 11, that is, a method using both a backlight having a relatively high directivity and the light diffusion layer is employed.
  • problems with the method using the viewing angle compensation film such as reduction of the color shift of the viewing angle caused by the passage of light at a large angle with respect to the normal direction (0 °) of the liquid crystal panel
  • a wide viewing angle can be realized.
  • the light diffusion layer according to the present invention contains a scatterer, it diffuses a relatively directional backlight and realizes a wide viewing angle. Further, since the light diffusion layer according to the present invention contains a colorant such as a pigment, it has a function of absorbing incident external light, and the light diffusion layer is located on the side farther from the backlight than the liquid crystal cell. Specifically, for example, as a (transparent) protective layer provided on the observer side or on the outside of the transparent protective layer, a decrease in contrast is suppressed.
  • FIG. 12 was taken of a liquid crystal display (right half side) with a PMMA polymer film (light diffusion layer) added with alumina fine particles added on the forefront and a liquid crystal display without the film (left half side). It is a photograph.
  • FIG. 12 (A) is taken in a state where the room is darkened and no external light hits the liquid crystal display
  • FIG. 12 (B) is a fluorescent lamp on the ceiling of the room, I'm shooting with the light hitting the LCD.
  • FIGS. 12A and 12B when a light diffusing layer is arranged on a liquid crystal display and exposed to external light, whitening occurs and contrast decreases (right side of FIG. 12B). .
  • the reason for whitening and lowering the contrast in FIG. 12B in which external light is applied is that the external light enters the light diffusion layer and scatters again. This is because the light returns to the outside (observer side) of the light diffusion layer.
  • FIG. 1 shows a first embodiment of such a light diffusion layer.
  • the scatterers 12 are dispersed in the translucent polymer 14, and more desirably, the scatterers 12 are uniformly distributed in the translucent polymer 14.
  • the translucent polymer 14 contains a colorant (not shown) such as a pigment.
  • the reason why return light due to external light that causes whitening can be attenuated by including a colorant in the light diffusion layer 10 is estimated as follows.
  • the present invention is not limited by such estimation.
  • the light reaching the observer's eyes out of the light from the backlight is light that has been scattered about once to several times and passed through the light diffusion layer 10.
  • the external light that reaches the eyes of the observer is light that has entered the light diffusion layer 10 and then repeatedly scattered more times by the scatterer 12 and returned to the observer side. Therefore, external light travels a longer distance in the light diffusion layer 10 than the light from the backlight (see the broken line arrow in FIG. 2).
  • the light diffusing layer 10 contains a colorant
  • external light traveling over a long distance is gradually absorbed by the colorant, and return light due to external light that causes whitening can be attenuated.
  • the configuration of the light diffusion layer is not limited to that shown in FIG. FIG. 3 shows a second embodiment of the light diffusion layer.
  • the scatterers 12 are distributed in the light diffusion layer 10 so as to be biased toward the liquid crystal layer in the thickness direction.
  • the scatterers 12 may be arranged at an appropriate interval, may be in contact with each other, or may be irregularly arranged.
  • FIG. 4 shows a third embodiment of the light diffusion layer.
  • the scatterers 12 are arranged in a plurality of layers in the thickness direction of the light diffusion layer.
  • the scatterer 12 does not necessarily have to form a regular layer.
  • FIG. 5 shows a fourth embodiment of the light diffusion layer.
  • a colored layer 18 including a light-transmitting polymer 14 and a colorant is provided on the outer side (observer side) of the scattering layer 16 including the light-transmitting polymer 14 and the scatterer 12.
  • the scattering layer 16 does not need to contain a colorant, but may contain it.
  • the external light observed as the return light can be obtained by using the light diffusing layer having the configuration of FIGS. Since the light travels a longer distance in the light diffusion layer, external light can be attenuated preferentially.
  • the light diffusion layer having the configuration shown in FIG. 5 can effectively attenuate external light.
  • the scattering layer 16 shown in FIG. 5 may have a distribution in which the scatterers 12 are biased in the film thickness direction as shown in FIGS. 3 and 4.
  • the outside of the light diffusion layer 10 may be subjected to antireflection or antiglare treatment using a known technique. It is also possible to introduce anti-glare particles 20 into the light diffusion layer 10 as shown in FIG.
  • organic dyes are suitable as the colorant, but organic pigments and inorganic pigments can also be used as long as they are miniaturized to such an extent that the resolution of the image is not significantly deteriorated and the dispersion state is good.
  • organic pigments and inorganic pigments such as carbon black, anthraquinone compounds, perylene compounds, disazo compounds, phthalocyanine compounds, isoindoline compounds, and dioxazine compounds can be used.
  • the kind of organic dye is not particularly limited.
  • the colorant may be used alone or in combination of a plurality of types.
  • the internal absorbance spectrum obtained by combining one or a plurality of light absorbers should ideally have substantially the same value over the entire wavelength range of visible light (about 380 nm to about 750 nm).
  • a cold cathode tube or an LED is often used, and usually has light intensity peaks at three main wavelengths corresponding to red (R), green (G), and blue (B). . Therefore, the light absorption of the dye added in the present invention does not necessarily have the same absorbance (transmittance) in the entire visible light wavelength region as described above, and is obtained by adjusting an appropriate absorbance balance in the three main wavelengths of the backlight. It may be.
  • the difference in internal absorbance of the light diffusion layer at the main wavelength of the light emitted from the backlight light source is as small as possible.
  • the difference is adjusted so that the difference between the internal absorbances of the light diffusion layers at wavelengths of about 435 nm, about 545 nm, and about 615 nm is as small as possible.
  • the difference between the internal absorbances of the light diffusion layers at the main wavelength of the light emitted from the backlight light source is preferably 0.05 or less, more preferably 0.02 or less, and 0 More preferably, it is .01 or less.
  • the main wavelengths of light emitted from the backlight light source are, for example, three wavelengths of about 435 nm, about 545 nm, and about 615 nm in a general cold cathode tube.
  • a light source having a main wavelength other than three wavelengths may be used as a backlight.
  • the four wavelengths are set as the main wavelengths.
  • an LED it may have a main wavelength different from that of the general cold cathode tube.
  • the main wavelength of the light emitted from the backlight light source does not greatly deviate even after passing through the light control means for controlling the directivity, but the main wavelength of the light after passing through the light control means
  • the internal absorbance of the light diffusion layer may be adjusted according to the above.
  • the color filter provided in the liquid crystal cell and the resin in each layer may attenuate light of a specific wavelength or shift the peak wavelength.
  • the internal absorbance of the light diffusion layer may be adjusted according to the main wavelength of the light immediately before entering the light diffusion layer, taking into account the spectrum of the light immediately before entering the light diffusion layer.
  • Table 1 shows the internal absorbance and transmittance of an example of the light scattering layer of the present invention, in which the internal absorbance is adjusted according to the main wavelength of a general cold cathode tube.
  • the internal absorbance of the light diffusion layer at the main wavelength of the light emitted from the backlight light source is adjusted to 0.014 or more. It is suitable, it is more preferable that it is 0.020 or more, and it is more preferable that it is 0.028 or more. Further, considering the front luminance, it is preferable to adjust the internal absorbance of the light diffusion layer at the main wavelength of the light emitted from the backlight light source to a range of 0.014 to 0.095.
  • it is in the range of 014 to 0.088, more preferably in the range of 0.020 to 0.088, still more preferably in the range of 0.028 to 0.088. More preferably, it is in the range of not less than 0.028 and not more than 0.062.
  • the light-transmitting polymer 14 and the scatterer 12 in the light diffusion layer are appropriately selected so that the combination of the respective refractive indexes and the size of the scatterer 12 have appropriate values.
  • the translucent polymer 14 used for the light diffusion layer a cellulose derivative typified by triacetyl cellulose, an acrylic polymer typified by polymethyl methacrylate, a cycloolefin polymer typified by polycarbonate, a norbornene-based polymer, etc.
  • Various translucent polymers can be used, but are not limited thereto.
  • the light-transmitting polymer 14 used in the light diffusion layer may be a homopolymer or a copolymer, or may be a blend of polymers. Further, these polymers may be high-purity polymers that hardly contain other additives, or may contain various additives such as plasticizers. Further, the translucent polymer 14 may be a polymer having adhesiveness.
  • the refractive index of the translucent polymer 14 is appropriately selected depending on the combination with the scatterer 12 and the like to be added, and thus is not generally specified, but is generally preferably 1.33 to 1.65. More preferably, it is 45 to 1.60.
  • the refractive index of triacetyl cellulose is 1.48
  • the refractive index of polymethyl methacrylate is 1.49.
  • translucent particles are suitable. Specifically, alumina particles, silicone polymer particles, melamine / formaldehyde condensate particles, benzoguanamine / formaldehyde condensate particles, benzoguanamine / melamine / formaldehyde condensate particles, titanium oxide particles, silica particles, etc. can be used. It is not limited to.
  • the average particle diameter of the scatterer 12 is appropriately selected depending on the combination with the above-described translucent polymer 14 and the like, and thus is not specified unconditionally. However, in general, it is preferably 0.05 ⁇ m or more and 25 ⁇ m or less. It is more preferably 1 ⁇ m or more and 20 ⁇ m or less, and further preferably 0.8 ⁇ m or more and 18 ⁇ m or less.
  • the refractive index of the scatterer is also not generally specified because it is appropriately selected depending on the combination with the above-described light-transmitting polymer, etc., but is generally 1.40 to 2.75, preferably 1.43 More preferably, it is ⁇ 1.9. Further, the refractive index of the scatterer 12 is preferably 0.02 to 1.25, more preferably 0.03 to 0.30, with respect to the refractive index of the translucent polymer 14. The refractive index difference in the above range is preferable from the viewpoint of the effect of light diffusion.
  • the content of the scatterer 12 with respect to the translucent polymer 14 is not generally specified because it is appropriately adjusted depending on the type of the translucent polymer 14 and the type and size of the scatterer 12.
  • the content is preferably from 50% by mass to 50% by mass, and more preferably from 0.5% by mass to 15% by mass.
  • the light diffusion layer according to the present invention has a function of diffusing light and a function of absorbing light.
  • the luminance of the backlight before entering the liquid crystal panel (corresponding to before entering the transparent protective layer 26 in FIG. 7) It can be evaluated by comparing the angular distribution and the angular distribution of luminance after the light from the backlight passes through the liquid crystal panel and is diffused by the light diffusion layer. More simply, it can be evaluated by measuring the haze (Haze) of a film sample obtained by adding a scatterer to a translucent polymer.
  • the haze is 70%.
  • the internal absorbance of the light diffusion layer at the main wavelength of light emitted from the backlight light source is 0.028 or more. It is preferable to adjust to 0.028 or more and 0.088 or less, more preferably 0.028 or more and 0.062 or less, and 0.055 or more and 0.062 or less. The following range is desirable from the viewpoint of maintaining high front luminance while displaying good black.
  • a backlight having lower directivity even a haze having a lower haze can be sufficiently diffused.
  • the haze is desirably 60% or more, and more desirably 70% or more.
  • the inside of the light diffusion layer at the main wavelength of light emitted from the backlight light source is used.
  • the absorbance is preferably adjusted to 0.020 or more, more preferably 0.020 or more and 0.095 or less, and further preferably 0.020 or more and 0.068 or less.
  • the range of 0.029 or more and 0.068 or less is desirable from the viewpoint of maintaining high front luminance while displaying good black.
  • the preferred haze value and the range of the internal absorbance are slightly different depending on the directivity of light from the backlight used, any directivity light can be used from the viewpoint of suppressing whitening of the screen.
  • any directivity light can be used from the viewpoint of suppressing whitening of the screen.
  • the effect can be obtained by adjusting the internal absorbance of the light diffusion layer to 0.014 or more.
  • the function of absorbing light can be evaluated by measuring the absorbance (or transmittance) with a commercially available measuring instrument.
  • a film sample in which a light absorbing agent is added to a translucent polymer is used.
  • the absorbance inside the film thus obtained is defined as internal absorbance.
  • the attenuation rate and transmittance are determined from the internal absorbance. These are defined as internal attenuation rate (%) and internal transmittance (%), respectively. The sum of the internal attenuation and the internal transmittance is 100%.
  • a light diffusion layer suitably designed based on the above evaluation results is installed in a transmissive liquid crystal display device having a configuration as shown in FIG. 7, and the effect is evaluated.
  • a coating solution containing a translucent polymer 14, a scatterer 12, and a colorant, and further containing a solvent or the like as necessary is prepared.
  • coating on the outermost layer in liquid crystal cells, such as transparent protective layer 26, is mentioned.
  • the transmissive liquid crystal display device of the present invention comprises at least a backlight light source, a light control means for controlling the directivity of light emitted from the backlight light source, and a transmissive type in order from the side closer to the light control means.
  • a liquid crystal cell ; and a light diffusion layer containing a light-transmitting polymer, a scatterer, and a colorant.
  • light emitted from the backlight light source 22 passes through the light guide plate 24 to become directional light, and this light is converted into a transparent protective layer 26, a polarizing film 28, a transparent protective layer 26, a glass substrate 30, It passes through the liquid crystal layer 32, the color filter 34, the glass substrate 30, the transparent protective layer 26, the polarizing film 28, and the transparent protective layer 26 and is diffused by the light diffusion layer 10.
  • the liquid crystal cell according to the present invention includes a transparent protective layer 26, a polarizing film 28, a transparent protective layer 26, a glass substrate 30, a liquid crystal layer 32, a color filter 34, a glass substrate 30, and transparent protection.
  • the layer 26, the polarizing film 28, and the transparent protective layer 26 are laminated in this order.
  • the present invention is not limited to this configuration, and it is sufficient that at least the liquid crystal layer 32 is provided.
  • the number of used members and the like can be appropriately selected, and other members may be provided.
  • the light diffusion layer 10 adjacent to the light diffusion layer 10 shown in FIG. 7 and the light diffusion layer 10 may be integrated, and the light diffusion layer may be used as the protection layer.
  • the transparent protective layer 26 and the light diffusing layer 10 are integrated and the light diffusing layer is also provided as a protective layer
  • the light diffusing layer is formed by a known film forming method such as a solution casting film forming method or a melt extrusion method. It can produce by producing as a film and bonding to the polarizing film 28 by a well-known method.
  • the scatterer 12 and a colorant may be added to an adhesive layer (not shown) for bonding the polarizing film 28 and the outer transparent protective layer 26, and this adhesive layer may be used as a light diffusion layer.
  • This pressure-sensitive adhesive layer contains a pressure-sensitive polymer, and this pressure-sensitive polymer is contained as a light-transmitting polymer.
  • the light diffusing layer 10 provided in the transmissive liquid crystal display device of the present invention only needs to contain a translucent polymer, a scatterer, and a colorant.
  • the light diffusing layer of the first embodiment shown in FIG. The light diffusion layer of the second embodiment shown in FIG. 3, the light diffusion layer of the third embodiment shown in FIG. 4, the light diffusion layer of the fourth embodiment shown in FIG. 5, and the antiglare particles 20 shown in FIG. Any of the light diffusing layers may be used.
  • the backlight light source 22 is preferably a cold cathode tube, but is not limited thereto, and a hot cathode tube, an LED, or the like can also be used. About LED, white LED may be used and red, green, and blue LED may be mixed and white may be produced. Further, a laser such as a laser diode can be used as a backlight light source. In particular, a laser that emits polarized light is suitable for the transmissive liquid crystal display device of the present invention because high efficiency can be obtained. Laser diodes, like LEDs, can mix several colors of light to create a white color.
  • the light guide plate 24 includes the backlight light source 22 and the light guide plate 24 as a light source unit, but other members may be additionally provided.
  • members such as a reflection sheet and a lamp reflector may be arranged around the light guide plate.
  • the light having directivity is made by the light guide plate 24, but the light directivity may be controlled by means other than the light guide plate.
  • a film having a function of condensing light on the diffusion plate 2 is provided by placing the cold cathode tubes at appropriate intervals and placing the diffusion plate 2 thereon. It is also possible to use a diffuser plate that is arranged or finely processed on the diffuser plate itself to have a light collecting function.
  • the directivity of light emitted from these elements is slightly lowered using a diffusion sheet or a diffusion plate. It can also be used. It is also possible to adjust the angle distribution with an appropriate luminance by appropriately combining light guide parts, light collecting parts, and light reflecting parts that are already used for lighting applications in these elements.
  • transmissive liquid crystal cell (liquid crystal layer) 32 As the transmissive liquid crystal cell (liquid crystal layer) 32, a known transmissive liquid crystal cell can be applied. Moreover, a well-known thing can also be applied suitably also about the transparent protective layer 26, the polarizing film 28, the glass substrate 30, and the color filter 34 which are used for the transmissive liquid crystal display device of this invention.
  • the transmission type liquid crystal display device of the present invention may use a viewing angle compensation film together with the light diffusion layer according to the present invention.
  • the transmissive liquid crystal display device using the light diffusion layer according to the present invention can realize a wide viewing angle without using a viewing angle compensation film. Furthermore, in the transmissive liquid crystal display device using the light diffusion layer according to the present invention, a decrease in contrast is suppressed.
  • Example 1 ⁇ Preparation of light diffusion layer> A single light diffusion layer as shown in FIG. 1 was produced by the method as described below. Triacetyl cellulose was added to methylene chloride, dissolved, and stirred uniformly to prepare a polymer solution. This solution was applied on a stainless steel substrate having a smooth surface and the solvent was volatilized to produce a transparent protective layer having a thickness of about 50 ⁇ m.
  • polymethylmethacrylate, red, blue and yellow organic dyes were added to methylene chloride, and alumina fine particles (average particle size 1.1 ⁇ m) were further added and stirred uniformly to prepare a dispersion.
  • the red, blue and yellow organic dyes were added so as to have the concentrations (mass%) shown in Table 2 below with respect to polymethyl methacrylate.
  • 10 mass parts of alumina fine particles were added with respect to 100 mass parts of polymethyl methacrylate.
  • the methylene chloride concentration was appropriately adjusted so that a light diffusion layer having a desired thickness was obtained and coating was easy. This dispersion was applied to the transparent protective layer to obtain light diffusion layers 11 to 14 having a thickness of about 30 ⁇ m.
  • a film (measurement sample) having a composition in which only the alumina fine particles were removed from the light diffusion layer having the above composition was prepared for measuring internal absorbance, internal attenuation, and internal transmittance.
  • the sample for measurement was prepared by first adding polymethylmethacrylate, red, blue and yellow organic dyes into methylene chloride and stirring uniformly to prepare a solution. This solution was applied onto a stainless steel substrate having a smooth surface, and the solvent was roughly volatilized to prepare measurement samples 11 to 14 having a thickness of about 30 ⁇ m.
  • the measurement samples 11 to 14 correspond to the light diffusion layers 11 to 14, respectively.
  • Internal absorbance, internal attenuation, and internal transmittance of the measurement samples 11 to 14 were measured using a commercially available spectrophotometer.
  • the internal absorbance is the absorbance of a film obtained by adding a light-absorbing substance without adding a scatterer such as alumina particles to a translucent polymer. It means absorbance due to light absorption inside the film without including reflection on the film surface.
  • the internal attenuation rate is an attenuation rate (%) converted from the internal absorbance.
  • FIG. 8 shows the internal absorbance spectrum of the measurement samples 11 to 14
  • FIG. 9 shows the internal transmittance spectrum of the measurement samples 11 to 14.
  • ⁇ Evaluation of haze> In order to evaluate the haze (cloudiness value) of the light diffusion layer, a polymer film (sample for haze measurement) in which only alumina fine particles having the same concentration (average particle diameter 1.1 ⁇ m) were added without adding an organic dye was prepared. did.
  • a polymer film sample for haze measurement
  • polymethyl methacrylate and alumina fine particles were added to methylene chloride, and stirred uniformly to prepare a dispersion. 10 mass parts of alumina fine particles were added with respect to 100 mass parts of polymethyl methacrylate.
  • a sample for haze measurement having a thickness of about 30 ⁇ m was obtained by applying this dispersion onto a stainless steel substrate having a smooth surface and volatilizing the solvent.
  • this haze measurement sample was measured with a haze meter (Nippon Denshoku Industries Co., Ltd., NDH2000), the haze was about 91%.
  • the light diffusing layers 11 to 14 were applied to the transmissive liquid crystal display device having the configuration shown in FIG. 7 for evaluation.
  • a VA type liquid crystal panel was used, and cold cathode tubes having principal wavelengths of about 435 nm, about 545 nm, and about 615 nm were used as a backlight light source.
  • the screen was illuminated with a fluorescent lamp from about 45 degrees obliquely in front of the screen so that the illuminance was about 100 lx, which was about the same level as a general living room, and the whitening of the screen was evaluated.
  • the screen was displayed in black during the evaluation. As a result, whitening was reduced as the sample had higher internal absorbance. If the internal absorbance is 0.014, it is practical, and if it is 0.028 or more, almost no whitening is observed. Particularly, samples 13 and 14 of 0.055 or more displayed good black.
  • a conventional liquid crystal panel provided with this viewing angle compensation film is a commercially available liquid crystal display, does not have a light diffusion layer, and does not have a layer to which a colorant as in the present invention is added. Since the screen of a conventional liquid crystal panel provided with a viewing angle compensation film has a full width at half maximum of the luminance angle distribution of about 70 degrees, the above results provide a sufficient viewing angle while using a highly directional backlight. Therefore, it was confirmed that the brightness angle distribution width necessary for this purpose was obtained.
  • the front luminance decreased as the concentration of the organic dye added increased. If the internal absorbance at the main wavelength of the light emitted from the backlight light source is 0.062 or less, the front luminance and luminance angle distribution width equal to or higher than the screen of a conventional liquid crystal panel having a viewing angle compensation film can be obtained. ing.
  • a conventional liquid crystal having a viewing angle compensation film as shown in FIG. 10 is formed by forming a light diffusion layer in which the internal absorbance at a main wavelength of light emitted from a backlight light source is about 0.062 or less.
  • a liquid crystal display having a front luminance and a luminance angle distribution width equal to or higher than the panel screen was obtained.
  • good characteristics were obtained in a light diffusion layer having an internal absorbance in the range of 0.028 to 0.062 at the main wavelength of light emitted from a backlight light source.
  • image blurring due to the light diffusion layer hardly occurred.
  • a viewing angle almost equivalent to the screen of a conventional liquid crystal panel including the viewing angle compensation film as shown in FIG. 10 was obtained.
  • Example 2 ⁇ Preparation of light diffusion layer> Single-layered light diffusion layers 21 to 24 as shown in FIG. 4 were produced by the following method. First, a transparent protective layer was prepared in the same manner as in Example 1. On the other hand, the same polymethylmethacrylate, red, blue and yellow organic dyes as in Example 1 were added to methylene chloride, and melamine / formaldehyde condensate fine particles (average particle size 1.3 ⁇ m) were further added. And a dispersion was prepared. The red, blue and yellow organic dyes were added so as to have the concentrations (mass%) shown in Table 4 below with respect to polymethyl methacrylate.
  • melamine formaldehyde condensate fine particles were added with respect to 100 mass parts of polymethyl methacrylate.
  • the methylene chloride concentration was appropriately adjusted so that a light diffusion layer having a desired thickness was obtained and coating was easy.
  • This dispersion was applied to the transparent protective layer to obtain a light diffusion layer having a thickness of about 30 ⁇ m.
  • the added light transmissive fine particles (melamine / formaldehyde condensate fine particles) are on one surface in the light diffusing layer as shown in FIG. It was confirmed that it was biased to the side.
  • ⁇ Evaluation of haze> In order to evaluate the haze of the light diffusing layer, a polymer film having a film thickness of about 30 ⁇ m (only a melamine / formaldehyde condensate fine particle having the same concentration (average particle size 1.3 ⁇ m) is added without adding an organic dye ( Sample for haze measurement) was prepared.
  • the method for producing the sample for haze measurement is in accordance with the method for producing the sample for haze measurement in Example 1. When the produced haze measurement sample was measured with a haze meter (Nippon Denshoku Industries Co., Ltd., NDH2000), the haze was about 94%.
  • the light diffusing layers 21 to 24 were added to the transmissive liquid crystal display element having the configuration shown in FIG. 7 to evaluate the light diffusing layers.
  • the liquid crystal panel was a VA type, and a cold cathode tube having principal wavelengths of about 435 nm, about 545 nm, and about 615 nm was used as the backlight.
  • the screen was illuminated with a fluorescent lamp from about 45 degrees obliquely in front of the screen so that the illuminance was about 100 lx, which was about the same level as a general living room, and the whitening of the screen was evaluated.
  • the screen was displayed in black. As a result, whitening was reduced as the sample had higher internal absorbance.
  • the internal absorbance at the main wavelength of the light emitted from the backlight light source is 0.014, it is practical, and if it is 0.028 or more, whitening is hardly observed, and in particular, it is emitted from the backlight light source. Good black was displayed for Sample 23 and Sample 24 having an internal absorbance of 0.055 or more at the main wavelength of light.
  • the screen of a conventional liquid crystal panel provided with a viewing angle compensation film has a full width at half maximum of the luminance angle distribution of about 70 degrees, the above results provide a sufficient viewing angle while using a highly directional backlight. Therefore, it was confirmed that the brightness angle distribution width necessary for this purpose was obtained.
  • the front luminance decreased as the concentration of the organic dye added increased. If the internal absorbance at the main wavelength of the light emitted from the backlight light source is 0.062 or less, the front luminance and luminance angle distribution width equal to or higher than the screen of a conventional liquid crystal panel having a viewing angle compensation film can be obtained. ing.
  • the light-transmitting polymer has a colorant on the outer side (observer side) of the light-diffusing layer having the laminated structure as shown in FIG. A layer in which a colored layer 18 to which is added was laminated was produced. Triacetyl cellulose was selected as the translucent polymer.
  • the red, blue and yellow organic dyes were added so as to have the concentrations (mass%) shown in Table 6 below with respect to triacetylcellulose.
  • the methylene chloride concentration was appropriately adjusted so that the desired film thickness was obtained and coating was easy.
  • the dispersion liquid-1 was applied to the transparent protective layer prepared in the same manner as in Example 1 to obtain a scattering layer 16 having a thickness of about 30 ⁇ m. Further, the solution-1 was applied on the scattering layer 16 to form a colored layer 18 having a thickness of about 30 ⁇ m, and light diffusion layers 31 to 34 were obtained.
  • ⁇ Evaluation of haze> In order to evaluate the haze of the light diffusion layer, a film (haze measurement sample) having the same composition as that of the scattering layer 16 of Example 3 was prepared.
  • the method for producing the sample for haze measurement is in accordance with the method for producing the sample for haze measurement in Example 1.
  • the produced haze measurement sample was measured with a haze meter (Nippon Denshoku Industries Co., Ltd., NDH2000), the haze was about 92%.
  • the light scattering layers 31 to 34 were applied to the transmissive liquid crystal display element having the configuration shown in FIG. 7 to evaluate the light diffusion layer.
  • the liquid crystal panel was a VA type, and a cold cathode tube having principal wavelengths of about 435 nm, about 545 nm, and about 615 nm was used as the backlight.
  • the screen was illuminated with a fluorescent lamp from about 45 degrees obliquely in front of the screen so that the illuminance was about 100 lx, which was about the same level as a general living room, and the whitening of the screen was evaluated.
  • the screen was displayed in black. As a result, whitening was reduced as the sample had higher internal absorbance.
  • the luminance distribution (Topcon Co., Ltd., BM-7FAST) was used to measure the front luminance and the angular distribution of luminance in the horizontal direction. The measurement was performed with the screen displayed in white.
  • the angular distribution of the luminance before entering the liquid crystal panel of the backlight used (equivalent to before entering the transparent protective layer 26 in FIG. 7) had a full width at half maximum of about 30 degrees. The light from the backlight passed through the liquid crystal panel and was diffused by the frontmost light diffusion layer. As a result, the full width at half maximum was about 70 degrees in any of the light diffusion layers.
  • the screen of a conventional liquid crystal panel equipped with a viewing angle compensation film has a full width at half maximum of the luminance angle distribution of about 70 degrees, so that a sufficient viewing angle can be obtained while using a highly directional backlight. It was confirmed that it had the necessary angular distribution width of luminance.
  • the front luminance was lower as the concentration of the organic dye added was higher. If the internal absorbance at the main wavelength of the light emitted from the backlight light source is 0.062 or less, the front luminance and luminance angle distribution width equal to or higher than the screen of a conventional liquid crystal panel having a viewing angle compensation film can be obtained. ing.
  • a viewing angle almost equivalent to the screen of a conventional liquid crystal panel including the viewing angle compensation film as shown in FIG. 10 can be obtained regardless of the configuration in which the viewing angle compensation film is not used. It was. Further, according to Examples 1 to 3, by forming a light diffusion layer corresponding to a range in which the internal absorbance at the main wavelength of the light emitted from the backlight light source is about 0.062 or less, whitening is favorably reduced.
  • a liquid crystal display having a front luminance and a luminance angle distribution width comparable to or higher than that of a screen of a conventional liquid crystal panel provided with a viewing angle compensation film as shown in FIG. 10 could be obtained.
  • Example 4 ⁇ Preparation of light diffusion layer> The light diffusion layers 41 to 45 were produced by the method as described below.
  • a transparent protective layer was prepared in the same manner as in Example 1.
  • CIPigment Red 48 3 (Sanyo Dye Co., Ltd.)
  • CIPigment Blue 15 1 (Copper Compound) (Sanyo Dye Co., Ltd.)
  • CIPigment Yellow 14 Sanyo Dyeing Co., Ltd.
  • alumina fine particles average particle size 1.1 ⁇ m
  • the red, blue and yellow organic pigments were added so as to have the concentration (mass%) shown in Table 8 below with respect to polymethyl methacrylate.
  • the alumina fine particles were added so as to be 5 parts by mass with respect to 100 parts by mass of polymethyl methacrylate.
  • the dispersion was appropriately adjusted in ethyl acetate concentration so that a light diffusion layer having a desired thickness was obtained and coating was easy. This dispersion was applied to the transparent protective layer to obtain light diffusion layers 41 to 45 having a thickness of about 30 ⁇ m.
  • Films (measurement samples 41 to 45) having a composition in which only the alumina fine particles were removed from the light diffusion layer having the above composition were prepared for measuring internal absorbance, internal attenuation, and internal transmittance.
  • the production method of the measurement samples 41 to 45 is in accordance with the production method of the measurement samples 11 to 14 in Example 1. These films were measured for internal absorbance, internal attenuation, and internal transmittance using a commercially available spectrophotometer.
  • ⁇ Evaluation of haze> In order to evaluate the haze of the light diffusing layer, a polymer film having a film thickness of about 30 ⁇ m (sample for haze measurement) in which only the alumina fine particles having the same concentration (average particle diameter 1.1 ⁇ m) are added without adding an organic dye. ) was produced.
  • the method for producing the sample for haze measurement is in accordance with the method for producing the sample for haze measurement in Example 1. When the produced haze measurement sample was measured with a haze meter (Nippon Denshoku Industries Co., Ltd., NDH2000), the haze was about 77%.
  • the light scattering layers 41 to 45 were added to the transmissive liquid crystal display element having the configuration shown in FIG. 7 to evaluate the light diffusion layer.
  • An IPS type liquid crystal panel was used, and cold cathode tubes having principal wavelengths of about 435 nm, about 545 nm, and about 615 nm were used as the backlight.
  • the screen was illuminated with a fluorescent lamp from 45 degrees obliquely in front of the screen to evaluate the whitening of the screen so that the illuminance is about 100 lx, which is about the same level as a general living room. During the evaluation, the screen was displayed in black. As a result, whitening was reduced as the sample had higher internal absorbance.
  • the internal absorbance at the main wavelength of the light emitted from the backlight source is 0.014, it is practical, and if it is 0.020 or more, almost no whitening is observed, and in particular, it is emitted from the backlight source.
  • the luminance angle distribution was measured in the same manner as in Example 1.
  • the luminance angle distribution measurement samples 41 and 42 as the light diffusion layer used for the measurement of the luminance angle distribution were added with an organic pigment in the amount shown in the sample 43 of Table 8 above, and the alumina fine particles were added to 100 mass of polymethyl methacrylate. It is added so that it may become 5 mass parts or 10 mass parts with respect to a part.
  • the luminance angle distribution before entering the liquid crystal panel of the backlight used (corresponding to before entering the transparent protective layer 26 in FIG. 7) had a full width at half maximum of about 47 degrees. As a result of the light from this backlight passing through the liquid crystal panel and being diffused by the frontmost light diffusion layer, as shown in Table 9, the full width at half maximum was about 70 degrees or more in any of the light diffusion layers. .
  • the screen of the conventional liquid crystal panel provided with the viewing angle compensation film has a full width at half maximum of the luminance angle distribution of about 70 degrees, when a backlight having a full width at half maximum of the luminance angle distribution of 47 degrees is used, the luminance It was confirmed that the angular distribution measurement sample 41 has an angular distribution width of luminance necessary for obtaining a sufficient viewing angle.
  • Example 4 when a backlight having a full width at half maximum of about 47 degrees in the luminance angle distribution is used, the internal absorbance at the main wavelength of the light emitted from the backlight source corresponds to a range of about 0.020 or more.
  • the light diffusion layer By forming the light diffusion layer, whitening was satisfactorily reduced, the viewing angle was sufficiently widened, and the full width at half maximum of luminance was about 70 degrees or more.
  • good characteristics were obtained when the internal absorbance at the main wavelength of light emitted from the backlight source was 0.029 or more. Further, in the liquid crystal display having the light diffusion layer of Example 4, image blurring due to the light diffusion layer hardly occurred.
  • Example 5 ⁇ Preparation of a light diffusion layer that also serves as a protective layer> A light diffusion layer 51 that also serves as a protective layer was produced by the method described below. The same polymethylmethacrylate and red, blue and yellow organic pigments as in Example 4 were added to ethyl acetate, and alumina fine particles (average particle size 1.1 ⁇ m) were further added, and the mixture was stirred and dispersed uniformly. A liquid was prepared. The alumina fine particles were added so as to be 20 parts by mass with respect to 100 parts by mass of polymethyl methacrylate.
  • CIPigment Red 48 3 (Sanyo Dye Co., Ltd.), CIPigment Blue 15: 1 (Copper Compound) (Sanyo Dye Co., Ltd.), CIPigment Yellow 14 (Sanyo Dye Co., Ltd.) )It was used.
  • the red, blue, and yellow organic pigments were added to 0.392 parts by mass, 0.072 parts by mass, and 0.120 parts by mass, respectively, with respect to 100 parts by mass of polymethyl methacrylate.
  • the dispersion was applied on a stainless steel substrate having a smooth surface, and the solvent was roughly dried to prepare a film sample.
  • the obtained film sample was pulverized and further dried under reduced pressure.
  • the obtained sample was mixed with 3 times the amount of polymethylmethacrylate pellets, kneaded using a twin screw extruder at 230 ° C., and then extruded into a film using a single screw extruder at 270 ° C. I wound up with.
  • the light diffusion layer 51 also serving as the protective layer was produced.
  • the light diffusing layer 51 that also serves as the protective layer of Example 5 is the same as the light diffusing layer 42 of Example 4 in the organic dye concentration and the addition amount of the alumina fine particles. It is thought that the same effect is produced.
  • a light diffusion layer 61 that also serves as a pressure-sensitive adhesive layer was produced by the method described below.
  • a solution having a concentration of about 30% by mass was prepared.
  • Coronate L manufactured by Nippon Polyurethane Co., Ltd. which is an isocyanate-based polyfunctional compound, is added to the acrylic polymer solution in an amount of 4 parts by mass with respect to 100 parts by mass of polymer solids, and additives (KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) 5 parts by mass, 5 parts by mass of alumina fine particles (average particle size 1.1 ⁇ m), and red, blue and yellow organic pigments were added to prepare an adhesive solution.
  • additives KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.
  • CIPigment Red 48 3 (Sanyo Dye Co., Ltd.)
  • CIPigment Blue 15 1 (Copper Compound) (Sanyo Dye Co., Ltd.)
  • CIPigment Yellow 14 Sanyo Dye Co., Ltd.
  • the red, blue and yellow organic pigments were added to 0.098 parts by mass, 0.018 parts by mass and 0.030 parts by mass with respect to 100 parts by mass of the copolymer.
  • a solvent for adjusting viscosity (ethyl acetate) is added, and the pressure-sensitive adhesive solution is placed on a release film (polyethylene terephthalate substrate: Diafoil MRF38, manufactured by Mitsubishi Chemical Polyester) so that the thickness after drying is 25 ⁇ m. After the application, it was dried in a hot air circulation oven to form an adhesive layer containing a scatterer and a colorant. The polarizing film 28 and the outer transparent protective layer 26 were bonded together using this pressure-sensitive adhesive layer.
  • a release film polyethylene terephthalate substrate: Diafoil MRF38, manufactured by Mitsubishi Chemical Polyester
  • the light diffusing layer 61 that also serves as the adhesive layer of Example 6 is the same as the light diffusing layer 42 of Example 4 in the organic dye concentration and the addition amount of the alumina fine particles. It is thought that the same effect is produced.

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Abstract

Disclosed is a transmission type liquid crystal display which comprises at least a backlight light source, a light control means for controlling the directivity of the light emitted from the backlight light source, a transmissive liquid crystal cell, and a light diffusion layer that contains a light-transmitting polymer, a scatterer and a coloring agent. The transmissive liquid crystal cell and the light diffusion layer are sequentially arranged in such a manner that the transmissive liquid crystal cell is closer to the light control means.

Description

透過型液晶表示装置Transmission type liquid crystal display device
 本発明は、透過型液晶表示装置に関するものである。 The present invention relates to a transmissive liquid crystal display device.
 透過型の液晶表示装置は、薄型・軽量・低消費電力といった優れた特長から、代表的なフラットパネルディスプレイとして広く用いられている。特にテレビ、パソコンのモニター、車載用ディスプレイ、携帯電話としての普及は著しい。液晶そのものは非発光なデバイスであるため、光源からの光の照射方式により、透過型、半透過反射型、反射型の3種に大別できる。比較的外光が弱い状況下などでは、安定的にバックライトから適切な強度の光を照射できる透過型の方式によって高い画質が実現される。したがって、テレビ、パソコンのモニターなどのように高い画質が要求される用途においては、主に透過型の液晶表示装置が用いられている。 The transmissive liquid crystal display device is widely used as a typical flat panel display because of its excellent features such as thinness, light weight and low power consumption. In particular, it has been widely used as a TV, personal computer monitor, in-vehicle display, and mobile phone. Since the liquid crystal itself is a non-light-emitting device, it can be roughly classified into three types, a transmission type, a transflective type, and a reflective type, depending on the light irradiation method from the light source. Under circumstances where the external light is relatively weak, high image quality is realized by a transmission type system that can stably emit light of appropriate intensity from the backlight. Therefore, transmissive liquid crystal display devices are mainly used in applications that require high image quality, such as televisions and personal computer monitors.
 液晶はその分子配列に関連してTNモード、VAモード、IPSモード、OCBモードなどがある。これらはそれぞれの光学的特性に起因する視野角依存性を有している。したがって、液晶パネルの法線方向(正面方向)においてコントラスト・色等の画質が良好となるように設計しても、斜め方向で画質が低下する。この問題を解決するために、図10に示すような視野角補償フィルムを用いる方法と、図11に示すような光拡散層を用いる方法が提案されている。 The liquid crystal has a TN mode, a VA mode, an IPS mode, an OCB mode and the like in relation to the molecular arrangement. These have a viewing angle dependency due to the respective optical characteristics. Accordingly, even when the image quality such as contrast and color is designed to be good in the normal direction (front direction) of the liquid crystal panel, the image quality is deteriorated in the oblique direction. In order to solve this problem, a method using a viewing angle compensation film as shown in FIG. 10 and a method using a light diffusion layer as shown in FIG. 11 have been proposed.
 視野角補償フィルムを用いる方法では、例えば図10に示すように、バックライト光源1から発せられた広角に光が広がったバックライトが、拡散板2を透過したのち、視野角補償フィルム3を備える液晶パネル4を通過する。 In the method using the viewing angle compensation film, for example, as shown in FIG. 10, the backlight having a wide angle emitted from the backlight light source 1 is transmitted through the diffuser plate 2 and then includes the viewing angle compensation film 3. Passes through the liquid crystal panel 4.
 このように、視野角補償フィルムを用いる方法では、光が広角に広がったバックライトを使用するので、光の一部は液晶パネル中の液晶層を斜めに通過する。それゆえ、液晶層を法線方向に通過する光と斜めに通過する光との位相差を補償するため、視野角補償フィルム3が使用される。現在市販されている液晶表示装置は、視野角補償フィルムを使用したものが多い。 As described above, in the method using the viewing angle compensation film, a backlight in which light spreads at a wide angle is used, so that part of the light passes obliquely through the liquid crystal layer in the liquid crystal panel. Therefore, the viewing angle compensation film 3 is used to compensate for the phase difference between the light passing through the liquid crystal layer in the normal direction and the light passing through the liquid crystal layer. Many liquid crystal display devices currently on the market use viewing angle compensation films.
 なお、図10では視野角補償フィルムを2枚使用した場合を示しているが、1枚のみ、あるいは3枚以上使用する場合もある。また、透明保護膜が視野角補償フィルムの機能を兼ねる場合もある。 Although FIG. 10 shows the case where two viewing angle compensation films are used, there are cases where only one or three or more are used. In some cases, the transparent protective film also serves as a viewing angle compensation film.
 この視野角補償フィルムは、高度な複屈折制御が必要とされるため、一般に他の光学フィルムに比べて高価である。また上述の液晶層を法線方向に通過する光と斜めに通過する光との位相差は、一般に波長に依存する。したがって、視野角補償フィルムは、使用する液晶層に適した複屈折の波長分散性を有するように調整する必要があるが、複屈折の波長分散性が物質固有の性質であるため、理想的な特性を有するものが容易に得られるわけではない。 Since this viewing angle compensation film requires a high degree of birefringence control, it is generally more expensive than other optical films. The phase difference between the light passing through the liquid crystal layer in the normal direction and the light passing obliquely depends on the wavelength. Therefore, the viewing angle compensation film needs to be adjusted to have birefringence wavelength dispersibility suitable for the liquid crystal layer to be used. Those having characteristics are not easily obtained.
 一方、光拡散層を用いる方法では、例えば図11に示すように、バックライト光源1から発せられ導光板6を通った光が、液晶パネル4、光拡散層5の順に、液晶表示パネルを凡そ法線方向に沿って通過する。 On the other hand, in the method using the light diffusing layer, for example, as shown in FIG. 11, the light emitted from the backlight source 1 and passing through the light guide plate 6 passes through the liquid crystal panel 4 and the light diffusing layer 5 in this order. Pass along the normal direction.
 このように、光拡散層を用いる方法では、指向性の高いバックライトと組み合わせて、殆どの光を凡そ法線方向に沿って液晶パネル中の液晶層を通過させるので、光の位相差を補償する視野角補償フィルムを設けなくともよく、また、液晶層を通過した後の光は光拡散層5によって広角に拡散するため、広い視野角を実現できる。 As described above, in the method using the light diffusion layer, in combination with the backlight having high directivity, most of the light passes through the liquid crystal layer in the liquid crystal panel almost along the normal direction, so that the phase difference of the light is compensated. It is not necessary to provide a viewing angle compensation film, and the light after passing through the liquid crystal layer is diffused to a wide angle by the light diffusion layer 5, so that a wide viewing angle can be realized.
 更に、光拡散層については、例えば、偏光板とガラス基板の間に透明な微粒子を敷き詰め、微粒子の隙間を透明な充填材によって埋めた光拡散層が提案されている(例えば、特許文献1参照。)。
 また、透明性樹脂中に散乱子が分散している光拡散フィルムを偏光板の保護フィルムとして用いる方法が提案されている(例えば、特許文献2参照。)。この特許文献2では、透明性樹脂中に分散した散乱子として、扁平状のものが記載されている。
Furthermore, for the light diffusion layer, for example, a light diffusion layer is proposed in which transparent fine particles are spread between a polarizing plate and a glass substrate, and the gaps between the fine particles are filled with a transparent filler (see, for example, Patent Document 1). .)
Further, a method has been proposed in which a light diffusion film in which scatterers are dispersed in a transparent resin is used as a protective film for a polarizing plate (for example, see Patent Document 2). In this patent document 2, a flat thing is described as a scatterer disperse | distributed in transparent resin.
 しかしながら、光拡散層を用いる方法は、外光によるコントラストの低下が問題となり、殆ど用いられていない。 However, the method using the light diffusing layer is hardly used because of a problem of a decrease in contrast due to external light.
 また視野角補償フィルムと光拡散層とを併用する方法も提案されている(例えば、特許文献3参照。)。この特許文献3では、主に液晶性化合物からなる視野角補償シートと光拡散層を併用し、OCBモードの視野角を改善する方法と、光学異方性を有するセルロースアセテートフィルムと光拡散層とを併用し、VAモードの視野角を改善する方法が記載されている。
 しかしながら、光拡散層における前述の問題については依然として解決されていない。
A method of using a viewing angle compensation film and a light diffusion layer in combination has also been proposed (see, for example, Patent Document 3). In Patent Document 3, a viewing angle compensation sheet mainly composed of a liquid crystalline compound and a light diffusing layer are used in combination to improve the OCB mode viewing angle, a cellulose acetate film having optical anisotropy, and a light diffusing layer. Is used together to improve the viewing angle of the VA mode.
However, the above-mentioned problem in the light diffusion layer has not been solved yet.
特許第3517975号明細書Japanese Patent No. 3517975 特許第3822102号明細書Japanese Patent No. 3822102 特許第第4054670号明細書Japanese Patent No. 4054670
 本発明は上記従来の事情に鑑みてなされたものであり、広い視野角を実現しつつ、外光によるコントラストの低下を抑制した透過型液晶表示装置を提供することを目的とする。 The present invention has been made in view of the above-described conventional circumstances, and an object of the present invention is to provide a transmissive liquid crystal display device that suppresses a decrease in contrast due to external light while realizing a wide viewing angle.
 請求項1に係る発明は、
 少なくとも、
 バックライト光源と、
 前記バックライト光源から発せられた光の指向性を制御する光制御手段と、
 前記光制御手段から近い側から順に、透過型の液晶セルと、透光性ポリマーと散乱子と着色剤とを含有する光拡散層と、
を有する透過型液晶表示装置である。
The invention according to claim 1
at least,
A backlight light source;
Light control means for controlling the directivity of light emitted from the backlight light source;
In order from the side closer to the light control means, a transmissive liquid crystal cell, a light diffusing layer containing a translucent polymer, a scatterer, and a colorant,
A transmissive liquid crystal display device having
 請求項2に係る発明は、
 前記光拡散層は、前記バックライト光源から発せられた光の主要波長における内部吸光度が0.014以上である請求項1に記載の透過型液晶表示装置である。
The invention according to claim 2
2. The transmissive liquid crystal display device according to claim 1, wherein the light diffusion layer has an internal absorbance of 0.014 or more at a main wavelength of light emitted from the backlight light source.
 請求項3に係る発明は、
 前記光拡散層は、前記バックライト光源から発せられた光の主要波長における内部吸光度が0.020以上である請求項1又は請求項2に記載の透過型液晶表示装置である。
The invention according to claim 3
The transmissive liquid crystal display device according to claim 1, wherein the light diffusion layer has an internal absorbance of 0.020 or more at a main wavelength of light emitted from the backlight light source.
 請求項4に係る発明は、
 前記光拡散層は、前記バックライト光源から発せられた光の主要波長における内部吸光度が0.028以上0.062以下である請求項1~請求項3のいずれか1項に記載の透過型液晶表示装置である。
The invention according to claim 4
The transmissive liquid crystal according to any one of claims 1 to 3, wherein the light diffusion layer has an internal absorbance of 0.028 or more and 0.062 or less at a main wavelength of light emitted from the backlight light source. It is a display device.
 請求項5に係る発明は、
 前記光拡散層中の前記散乱子の含有濃度が、前記光拡散層の膜厚方向において前記液晶セル側で高い請求項1~請求項4のいずれか1項に記載の透過型液晶表示装置である。
The invention according to claim 5
5. The transmissive liquid crystal display device according to claim 1, wherein a concentration of the scatterer in the light diffusion layer is high on the liquid crystal cell side in a film thickness direction of the light diffusion layer. is there.
 請求項6に係る発明は、
 前記光拡散層が、前記透光性ポリマー中に前記光散乱子が分散された散乱層と、前記透光性ポリマー及び前記着色剤を含有する着色層と、の積層体である請求項1~請求項5のいずれか1項に記載の透過型液晶表示装置である。
The invention according to claim 6
The light diffusion layer is a laminate of a scattering layer in which the light scatterers are dispersed in the light-transmitting polymer and a colored layer containing the light-transmitting polymer and the colorant. The transmissive liquid crystal display device according to claim 5.
 本発明によれば、広い視野角を実現しつつ、外光によるコントラストの低下を抑制した透過型液晶表示装置を提供することができる。 According to the present invention, it is possible to provide a transmissive liquid crystal display device that realizes a wide viewing angle and suppresses a decrease in contrast due to external light.
第一の実施形態の光拡散層の断面概略図である。It is a section schematic diagram of the light diffusion layer of a first embodiment. 本発明に係る光拡散層の作用・機能を説明する図である。It is a figure explaining the effect | action and function of the light-diffusion layer which concerns on this invention. 第二の実施形態の光拡散層の断面概略図である。It is a section schematic diagram of a light diffusion layer of a second embodiment. 第三の実施形態の光拡散層の断面概略図である。It is the cross-sectional schematic of the light-diffusion layer of 3rd embodiment. 第四の実施形態の光拡散層の断面概略図である。It is the cross-sectional schematic of the light-diffusion layer of 4th embodiment. 他の実施形態の光拡散層の断面概略図である。It is the cross-sectional schematic of the light-diffusion layer of other embodiment. 本発明の透過型液晶表示装置における一例の構成を示す断面概略図である。1 is a schematic cross-sectional view illustrating an exemplary configuration of a transmissive liquid crystal display device of the present invention. 実施例1における試料11~14の内部吸光度スペクトルである。2 is an internal absorbance spectrum of Samples 11 to 14 in Example 1. 実施例1における試料11~14の内部透過率スペクトルである。3 is an internal transmittance spectrum of Samples 11 to 14 in Example 1. 従来の視野角補償フィルムを用いた液晶ディスプレイでの光の通過経路を説明する図である。It is a figure explaining the passage route of the light in the liquid crystal display using the conventional viewing angle compensation film. 一般的な光拡散層を用いた液晶ディスプレイでの光の通過経路を説明する図である。It is a figure explaining the passage route of the light in the liquid crystal display using a general light-diffusion layer. 従来の光拡散層による外光の影響を示す写真であり、(A)は外光なし、(B)は外光ありの状態で撮影した写真である。It is the photograph which shows the influence of the external light by the conventional light-diffusion layer, (A) is a photograph image | photographed in the state with no external light, (B) with external light.
 本発明の透過型液晶表示装置は、少なくとも、バックライト光源と、前記バックライト光源から発せられた光の指向性を制御する光制御手段と、前記光制御手段から近い側から順に、透過型の液晶セルと、透光性ポリマーと散乱子と着色剤とを含有する光拡散層と、を有する。 The transmissive liquid crystal display device of the present invention comprises at least a backlight light source, a light control means for controlling the directivity of light emitted from the backlight light source, and a transmissive type in order from the side closer to the light control means. A liquid crystal cell; and a light diffusion layer containing a light-transmitting polymer, a scatterer, and a colorant.
 一般的には、液晶ディスプレイの視野角による色シフトを低減するために、図10に示したような視野角補償フィルムが用いられている。この視野角補償フィルムには適切な複屈折の波長分散を付与する必要がある。しかしながら、複屈折の波長分散は材料に固有の特性であり、理想的な波長分散性を有するポリマーを得ることは容易ではない。 Generally, a viewing angle compensation film as shown in FIG. 10 is used in order to reduce a color shift due to a viewing angle of a liquid crystal display. The viewing angle compensation film must be provided with appropriate birefringence wavelength dispersion. However, birefringence wavelength dispersion is a characteristic inherent to the material, and it is not easy to obtain a polymer having ideal wavelength dispersion.
 そこで、本発明では、図11に示す光拡散層を用いる方法、つまり比較的指向性が高いバックライトと光拡散層とを併用する方法を採用する。この方法を採用することで、液晶パネルの法線方向(0°)に対して大きな角度で光が通過するために生じる視野角の色シフトの低減など、視野角補償フィルムを用いる方法での問題が解消された上、広視野角を実現できる。 Therefore, in the present invention, a method using the light diffusion layer shown in FIG. 11, that is, a method using both a backlight having a relatively high directivity and the light diffusion layer is employed. By adopting this method, problems with the method using the viewing angle compensation film, such as reduction of the color shift of the viewing angle caused by the passage of light at a large angle with respect to the normal direction (0 °) of the liquid crystal panel In addition, a wide viewing angle can be realized.
 本発明に係る光拡散層は散乱子を含有するため、比較的指向性を有するバックライトを拡散させ、広い視野角を実現する。また、本発明に係る光拡散層は色素等の着色剤を含有するため、入射した外光を吸収する機能を有しており、この光拡散層を前記液晶セルよりも前記バックライトから遠い側、具体的には例えば観察者側に付設された(透明)保護層として或いは該透明保護層の外側、に付与することにより、コントラストの低下が抑制される。 Since the light diffusion layer according to the present invention contains a scatterer, it diffuses a relatively directional backlight and realizes a wide viewing angle. Further, since the light diffusion layer according to the present invention contains a colorant such as a pigment, it has a function of absorbing incident external light, and the light diffusion layer is located on the side farther from the backlight than the liquid crystal cell. Specifically, for example, as a (transparent) protective layer provided on the observer side or on the outside of the transparent protective layer, a decrease in contrast is suppressed.
 ここで、本発明の機能・作用を説明するため、まず始めに、従来の光拡散層を用いた液晶ディスプレイの実状を説明する。 Here, in order to explain the function and operation of the present invention, first, the actual state of a liquid crystal display using a conventional light diffusion layer will be described.
 図12は、アルミナ微粒子を添加したPMMAポリマーフィルム(光拡散層)を最前面に設置した液晶ディスプレイ(右半分側)と、該フィルムを配置していない液晶ディスプレイ(左半分側)とを撮影した写真である。
 ここで、図12(A)は、部屋を暗くし外光が液晶ディスプレイに当たらない状態で撮影しており、一方、図12(B)は、部屋の天井部分にある蛍光灯を点灯させ、その光が液晶ディスプレイへ当たっている状態で撮影している。
FIG. 12 was taken of a liquid crystal display (right half side) with a PMMA polymer film (light diffusion layer) added with alumina fine particles added on the forefront and a liquid crystal display without the film (left half side). It is a photograph.
Here, FIG. 12 (A) is taken in a state where the room is darkened and no external light hits the liquid crystal display, while FIG. 12 (B) is a fluorescent lamp on the ceiling of the room, I'm shooting with the light hitting the LCD.
 図12(A)と(B)とを比べると明らかなように、液晶ディスプレイに光拡散層を配置して外光を当てると、白化してコントラストが低下する(図12(B)の右側)。外光を当てない図12(A)の場合に比べて、外光を当てた図12(B)において白化しコントラストが低下する理由は、外光が光拡散層に入り込み散乱した後に、再度その光が光拡散層の外側(観察者側)へ戻ることによる。 As is clear from comparison between FIGS. 12A and 12B, when a light diffusing layer is arranged on a liquid crystal display and exposed to external light, whitening occurs and contrast decreases (right side of FIG. 12B). . Compared to the case of FIG. 12A in which no external light is applied, the reason for whitening and lowering the contrast in FIG. 12B in which external light is applied is that the external light enters the light diffusion layer and scatters again. This is because the light returns to the outside (observer side) of the light diffusion layer.
 このように従来の光拡散層を用いた液晶ディスプレイでは、外光の入り込みによるコントラストの低下の問題が存在していた。 As described above, in the conventional liquid crystal display using the light diffusion layer, there is a problem of a decrease in contrast due to the entrance of external light.
 上記状況において、本発明者らは、透光性ポリマー中に、光を拡散させるための散乱子と光を吸収するための色素等の着色剤とを添加した光拡散層により、画像の精細さをほぼ維持し、外光による白化を抑制しつつ、バックライトからの光を広角に広げることができることを明らかにした。このような光拡散層の第一の実施態様として図1を示す。
 図1では、光拡散層10において、散乱子12は透光性ポリマー14中に分散されており、より望ましくは散乱子12が透光性ポリマー14中に均一に分布している場合である。更に透光性ポリマー14は、色素等の着色剤(図示せず)を含有する。
In the above situation, the present inventors have developed a fine image by using a light diffusing layer in which a scatterer for diffusing light and a colorant such as a dye for absorbing light are added in a translucent polymer. It has been clarified that the light from the backlight can be expanded to a wide angle while maintaining whiteness and suppressing whitening due to external light. FIG. 1 shows a first embodiment of such a light diffusion layer.
In FIG. 1, in the light diffusion layer 10, the scatterers 12 are dispersed in the translucent polymer 14, and more desirably, the scatterers 12 are uniformly distributed in the translucent polymer 14. Furthermore, the translucent polymer 14 contains a colorant (not shown) such as a pigment.
 ここで、光拡散層10に着色剤を含有させることで、白化の原因となる外光による戻り光を減衰させることができる理由を以下のように推測する。但し、このような推測によって本発明は限定されない。 Here, the reason why return light due to external light that causes whitening can be attenuated by including a colorant in the light diffusion layer 10 is estimated as follows. However, the present invention is not limited by such estimation.
 図2の実線矢印に示すように、バックライトからの光のうち観測者の目に到達するものは、おおよそ1回~数回程度散乱されて光拡散層10を通過した光である。これに対し、外光のうち観測者の目に到達するものは、光拡散層10に進入した後、散乱子12によってより多くの回数の散乱を繰り返し観測者側に戻った光である。よって、外光は、バックライトからの光に比べて光拡散層10中で長い距離を進む(図2の破線矢印参照)。 As shown by the solid line arrow in FIG. 2, the light reaching the observer's eyes out of the light from the backlight is light that has been scattered about once to several times and passed through the light diffusion layer 10. On the other hand, the external light that reaches the eyes of the observer is light that has entered the light diffusion layer 10 and then repeatedly scattered more times by the scatterer 12 and returned to the observer side. Therefore, external light travels a longer distance in the light diffusion layer 10 than the light from the backlight (see the broken line arrow in FIG. 2).
 ここで、光拡散層10に着色剤を含有させると、長い距離を進行する外光は着色剤によって次第に吸収され、白化の原因となる外光による戻り光を減衰させることができる。 Here, when the light diffusing layer 10 contains a colorant, external light traveling over a long distance is gradually absorbed by the colorant, and return light due to external light that causes whitening can be attenuated.
 上述のような基本原理を鑑みれば、光拡散層の構成は図1に示すようなものに限らない。光拡散層の第二の実施態様として図3を示す。
 図3では、散乱子12が光拡散層10中、厚さ方向において液晶層側に偏って分布している。散乱子12同士は適当な間隔で並んでいても良いし、接していてもよく、不規則に配列していてもよい。
In view of the basic principle as described above, the configuration of the light diffusion layer is not limited to that shown in FIG. FIG. 3 shows a second embodiment of the light diffusion layer.
In FIG. 3, the scatterers 12 are distributed in the light diffusion layer 10 so as to be biased toward the liquid crystal layer in the thickness direction. The scatterers 12 may be arranged at an appropriate interval, may be in contact with each other, or may be irregularly arranged.
 また、光拡散層の第三の実施態様として図4を示す。
 図4では、散乱子12は光拡散層の厚さ方向に複数層をなすように配列している。散乱子12は必ずしも規則的な層状を形成していなくてもよい。
FIG. 4 shows a third embodiment of the light diffusion layer.
In FIG. 4, the scatterers 12 are arranged in a plurality of layers in the thickness direction of the light diffusion layer. The scatterer 12 does not necessarily have to form a regular layer.
 更に、光拡散層の第四の実施態様として図5を示す。
 図5では、透光性ポリマー14と散乱子12とを含む散乱層16の外側(観察者側)に、透光性ポリマー14と着色剤とを含む着色層18を設けている。散乱層16は着色剤を含有しなくてもよいが、含有させても構わない。
Further, FIG. 5 shows a fourth embodiment of the light diffusion layer.
In FIG. 5, a colored layer 18 including a light-transmitting polymer 14 and a colorant is provided on the outer side (observer side) of the scattering layer 16 including the light-transmitting polymer 14 and the scatterer 12. The scattering layer 16 does not need to contain a colorant, but may contain it.
 図2に示した、バックライトと外光のそれぞれの進行経路から明らかなように、図3、図4及び図5の構成の光拡散層にすることによって、戻り光として観察される外光は、光拡散層内でより長い距離を進行することになるため、外光を優先的に減衰させることができる。特に、図5の構成の光拡散層は、外光を効果的に減衰させることができる。
 更に、図5に示す散乱層16は、図3及び図4のように散乱子12が膜厚方向に偏った分布をしていてもよい。
As apparent from the respective traveling paths of the backlight and the external light shown in FIG. 2, the external light observed as the return light can be obtained by using the light diffusing layer having the configuration of FIGS. Since the light travels a longer distance in the light diffusion layer, external light can be attenuated preferentially. In particular, the light diffusion layer having the configuration shown in FIG. 5 can effectively attenuate external light.
Further, the scattering layer 16 shown in FIG. 5 may have a distribution in which the scatterers 12 are biased in the film thickness direction as shown in FIGS. 3 and 4.
 光拡散層10の外側には、公知の技術を用いて反射防止やアンチグレア処理を施してもよい。また図6のように光拡散層10にアンチグレア用粒子20を導入することも可能である。 The outside of the light diffusion layer 10 may be subjected to antireflection or antiglare treatment using a known technique. It is also possible to introduce anti-glare particles 20 into the light diffusion layer 10 as shown in FIG.
 以下、光拡散層を構成する成分について説明する。
 着色剤は、各種有機色素が好適であるが、画像の解像度を著しく劣化させない程度に微細化されて、かつ分散状態が良好であれば、有機顔料、無機顔料も使用できる。具体的には、カーボンブラック、アントラキノン系化合物、ペリレン系化合物、ジスアゾ系化合物、フタロシアニン系化合物、イソインドリン系化合物、ジオキサジン系化合物など公知の有機顔料、無機顔料を使用できる。有機色素の種類は特に限定されない。
Hereinafter, components constituting the light diffusion layer will be described.
Various organic dyes are suitable as the colorant, but organic pigments and inorganic pigments can also be used as long as they are miniaturized to such an extent that the resolution of the image is not significantly deteriorated and the dispersion state is good. Specifically, known organic pigments and inorganic pigments such as carbon black, anthraquinone compounds, perylene compounds, disazo compounds, phthalocyanine compounds, isoindoline compounds, and dioxazine compounds can be used. The kind of organic dye is not particularly limited.
 着色剤は、一種類のものを単独で使用しても、複数の種類のものを組み合わせて使用してもよい。光吸収剤を一種類あるいは複数組み合わせて得られる内部吸光度のスペクトルは、理想的には、可視光の波長域(約380nm~約750nm)の全域に渡って略同じ値であることが望ましい。 The colorant may be used alone or in combination of a plurality of types. Ideally, the internal absorbance spectrum obtained by combining one or a plurality of light absorbers should ideally have substantially the same value over the entire wavelength range of visible light (about 380 nm to about 750 nm).
 液晶ディスプレイのバックライト光源としては、冷陰極管またはLEDが用いられることが多く、通常、赤(R)、緑(G)、青(B)に相当する主要3波長に光強度のピークを有する。したがって、本発明において添加する色素の光吸収は、上述のように可視光波長域全域において必ずしも同じ吸光度(透過率)でなくともよく、バックライトの主要3波長において適切な吸光度バランスを調整したものであってもよい。 As a backlight source of a liquid crystal display, a cold cathode tube or an LED is often used, and usually has light intensity peaks at three main wavelengths corresponding to red (R), green (G), and blue (B). . Therefore, the light absorption of the dye added in the present invention does not necessarily have the same absorbance (transmittance) in the entire visible light wavelength region as described above, and is obtained by adjusting an appropriate absorbance balance in the three main wavelengths of the backlight. It may be.
 良好な白色を表示させる観点からは、バックライト光源から発せられた光の主要波長における光拡散層の各内部吸光度の差がなるべく小さくなるよう調整することが望ましい。例えば、光源として主要波長が3波長型の冷陰極管を用いた場合、約435nm、約545nm及び約615nmの波長における光拡散層の各内部吸光度の間で、差がなるべく小さくなるよう調整することが好ましい。
 具体的には、バックライト光源から発せられた光の主要波長における光拡散層の各内部吸光度の差は、0.05以下であることが好ましく、0.02以下であることがより好ましく、0.01以下であることが更に好ましい。
From the viewpoint of displaying a good white color, it is desirable to adjust so that the difference in internal absorbance of the light diffusion layer at the main wavelength of the light emitted from the backlight light source is as small as possible. For example, when a cold cathode tube with a three-wavelength main wavelength is used as the light source, the difference is adjusted so that the difference between the internal absorbances of the light diffusion layers at wavelengths of about 435 nm, about 545 nm, and about 615 nm is as small as possible. Is preferred.
Specifically, the difference between the internal absorbances of the light diffusion layers at the main wavelength of the light emitted from the backlight light source is preferably 0.05 or less, more preferably 0.02 or less, and 0 More preferably, it is .01 or less.
 ここで、バックライト光源から発せられた光の主要波長とは、例えば、一般的な冷陰極管では約435nm、約545nm、約615nmの3波長をいう。また、主要波長が3波長以外の光源がバックライトとして用いられる場合もある。例えば、青・緑・赤の3波長に深紅を加えた4波長バックライトなども存在するので、この場合には当該4波長を主要波長とする。更に、LEDの場合には上記一般的な冷陰極管とは異なる主要波長を有する場合がある。 Here, the main wavelengths of light emitted from the backlight light source are, for example, three wavelengths of about 435 nm, about 545 nm, and about 615 nm in a general cold cathode tube. In addition, a light source having a main wavelength other than three wavelengths may be used as a backlight. For example, there is a four-wavelength backlight in which crimson is added to three wavelengths of blue, green, and red. In this case, the four wavelengths are set as the main wavelengths. Furthermore, in the case of an LED, it may have a main wavelength different from that of the general cold cathode tube.
 なお、バックライト光源から発せられた光の主要波長は、その指向性を制御するための光制御手段を通過した後においても大きくずれることはないが、光制御手段の通過後の光の主要波長に合わせて光拡散層の内部吸光度を調整してもよい。
 また、液晶セルに設けられたカラーフィルターや各層中の樹脂によって、特定波長の光が減衰したり、ピーク波長がずれたりする場合がある。この場合には、光拡散層に入射する直前の光のスペクトルを勘案し、光拡散層に入射する直前の光の主要波長に合わせて光拡散層の内部吸光度を調整してもよい。
The main wavelength of the light emitted from the backlight light source does not greatly deviate even after passing through the light control means for controlling the directivity, but the main wavelength of the light after passing through the light control means The internal absorbance of the light diffusion layer may be adjusted according to the above.
In addition, the color filter provided in the liquid crystal cell and the resin in each layer may attenuate light of a specific wavelength or shift the peak wavelength. In this case, the internal absorbance of the light diffusion layer may be adjusted according to the main wavelength of the light immediately before entering the light diffusion layer, taking into account the spectrum of the light immediately before entering the light diffusion layer.
 表1に、一般的な冷陰極管の主要波長に合わせて内部吸光度を調整した、本発明の光散乱層の一例における内部吸光度及び透過率を示す。 Table 1 shows the internal absorbance and transmittance of an example of the light scattering layer of the present invention, in which the internal absorbance is adjusted according to the main wavelength of a general cold cathode tube.
Figure JPOXMLDOC01-appb-T000001

 
Figure JPOXMLDOC01-appb-T000001

 
 表1に示すように、光源として用いたバックライト光源から発せられた光の主要波長を考慮して、この主要波長での光拡散層の各内部吸光度の差が小さくなるよう調整することが望ましい。 As shown in Table 1, in consideration of the main wavelength of the light emitted from the backlight light source used as the light source, it is desirable to adjust so that the difference in each internal absorbance of the light diffusion layer at this main wavelength becomes small. .
 一方、バックライトからの光は、なるべく光拡散層10中の着色剤に吸収されることなく透過して観察者に届くことが輝度を高める観点から望ましい。よって、光拡散層10中の着色剤の含有量は、外光による戻り光を減衰させつつバックライトからの光の損失を抑えるような吸光度の範囲となるように調整することが望ましい。 On the other hand, it is desirable from the viewpoint of increasing luminance that the light from the backlight is transmitted as much as possible without being absorbed by the colorant in the light diffusion layer 10 and reaches the observer. Therefore, it is desirable to adjust the content of the colorant in the light diffusion layer 10 so as to fall within an absorbance range that suppresses the loss of light from the backlight while attenuating return light due to external light.
 そこで、外光を減衰させ且つバックライトからの光の減衰を抑えるという本発明の目的からは、バックライト光源から発せられた光の主要波長における光拡散層の内部吸光度を0.014以上に調整することが好適であり、0.020以上であることがより好ましく、0.028以上であることがより好ましい。更に正面輝度を考慮すれば、バックライト光源から発せられた光の主要波長における光拡散層の内部吸光度を0.014以上0.095以下の範囲の範囲に調整することが好適であり、0.014以上0.088以下の範囲であることがより好ましく、0.020以上0.088以下の範囲であることが更に好ましく、0.028以上0.088以下の範囲であることが更に好ましく、0.028以上0.062以下の範囲であることが更に好ましい。 Therefore, for the purpose of the present invention to attenuate the external light and suppress the attenuation of the light from the backlight, the internal absorbance of the light diffusion layer at the main wavelength of the light emitted from the backlight light source is adjusted to 0.014 or more. It is suitable, it is more preferable that it is 0.020 or more, and it is more preferable that it is 0.028 or more. Further, considering the front luminance, it is preferable to adjust the internal absorbance of the light diffusion layer at the main wavelength of the light emitted from the backlight light source to a range of 0.014 to 0.095. More preferably, it is in the range of 014 to 0.088, more preferably in the range of 0.020 to 0.088, still more preferably in the range of 0.028 to 0.088. More preferably, it is in the range of not less than 0.028 and not more than 0.062.
 光拡散層中の透光性ポリマー14及び散乱子12は、それぞれの屈折率の組み合わせや、散乱子12の大きさが適切な値になるよう適宜選択することが望ましい。これらの調整により散乱子12によってバックライトからの光が散乱されて広角な視野角を実現し、且つ効率良く光拡散層を通過して高い輝度を呈する。更には、これらの調整により、光拡散層を付設したことによる画像の呆けを抑制することができる。 It is desirable that the light-transmitting polymer 14 and the scatterer 12 in the light diffusion layer are appropriately selected so that the combination of the respective refractive indexes and the size of the scatterer 12 have appropriate values. With these adjustments, light from the backlight is scattered by the scatterer 12 to realize a wide viewing angle, and efficiently pass through the light diffusion layer to exhibit high luminance. Furthermore, by these adjustments, image blur due to the addition of the light diffusion layer can be suppressed.
 具体的に、光拡散層に用いる透光性ポリマー14としては、トリアセチルセルロースに代表されるセルロース誘導体、ポリメチルメタクリレートに代表されるアクリルポリマー、ポリカーボネートに代表されるシクロオレフィンポリマー、ノルボルネン系ポリマーなど種々の透光性ポリマーを用いることが可能であるが、これらに限定されない。また光拡散層に用いる透光性ポリマー14はホモポリマーあるいは共重合ポリマーであってもよいし、ポリマーをブレンドしたものを用いてもよい。さらにこれらのポリマーは、他の添加物をほとんど含まない純度の高いポリマーであってもよいし、可塑剤等の各種添加物を含んでもよい。更にこの透光性ポリマー14は粘着性を有するポリマーであってもよい。 Specifically, as the translucent polymer 14 used for the light diffusion layer, a cellulose derivative typified by triacetyl cellulose, an acrylic polymer typified by polymethyl methacrylate, a cycloolefin polymer typified by polycarbonate, a norbornene-based polymer, etc. Various translucent polymers can be used, but are not limited thereto. The light-transmitting polymer 14 used in the light diffusion layer may be a homopolymer or a copolymer, or may be a blend of polymers. Further, these polymers may be high-purity polymers that hardly contain other additives, or may contain various additives such as plasticizers. Further, the translucent polymer 14 may be a polymer having adhesiveness.
 透光性ポリマー14の屈折率は、添加する散乱子12等との組み合わせにより適宜選択するので一概には特定されないが、一般的には1.33~1.65であることが好ましく、1.45~1.60であることがより好ましい。例えば、トリアセチルセルロースの屈折率は、1.48であり、ポリメチルメタクリレートの屈折率は、1.49である。 The refractive index of the translucent polymer 14 is appropriately selected depending on the combination with the scatterer 12 and the like to be added, and thus is not generally specified, but is generally preferably 1.33 to 1.65. More preferably, it is 45 to 1.60. For example, the refractive index of triacetyl cellulose is 1.48, and the refractive index of polymethyl methacrylate is 1.49.
 散乱子12としては、透光性の粒子が好適である。具体的には、アルミナ粒子、シリコーンポリマー粒子、メラミン・ホルムアルデヒド縮合物粒子、ベンゾグアナミン・ホルムアルデヒド縮合物粒子、ベンゾグアナミン・メラミン・ホルムアルデヒド縮合物粒子、酸化チタン粒子、シリカ粒子などが使用可能であるが、これらに限定されない。 As the scatterer 12, translucent particles are suitable. Specifically, alumina particles, silicone polymer particles, melamine / formaldehyde condensate particles, benzoguanamine / formaldehyde condensate particles, benzoguanamine / melamine / formaldehyde condensate particles, titanium oxide particles, silica particles, etc. can be used. It is not limited to.
 散乱子12の平均粒径は、上述の透光性ポリマー14等との組み合わせにより適宜選択するので一概には特定されないが、一般的には0.05μm以上25μm以下であることが好ましく、0.1μm以上20μm以下であることがより好ましく、0.8μm以上18μm以下であることが更に好ましい。 The average particle diameter of the scatterer 12 is appropriately selected depending on the combination with the above-described translucent polymer 14 and the like, and thus is not specified unconditionally. However, in general, it is preferably 0.05 μm or more and 25 μm or less. It is more preferably 1 μm or more and 20 μm or less, and further preferably 0.8 μm or more and 18 μm or less.
 散乱子の屈折率についても、上述の透光性ポリマー等との組み合わせにより適宜選択するので一概には特定されないが、一般的には1.40~2.75であることが好ましく、1.43~1.9であることがより好ましい。また、散乱子12の屈折率は、透光性ポリマー14の屈折率との差が、0.02~1.25であることが好ましく、0.03~0.30であることがより好ましい。上記範囲の屈折率差は、光拡散の効果の観点から好適である。 The refractive index of the scatterer is also not generally specified because it is appropriately selected depending on the combination with the above-described light-transmitting polymer, etc., but is generally 1.40 to 2.75, preferably 1.43 More preferably, it is ˜1.9. Further, the refractive index of the scatterer 12 is preferably 0.02 to 1.25, more preferably 0.03 to 0.30, with respect to the refractive index of the translucent polymer 14. The refractive index difference in the above range is preferable from the viewpoint of the effect of light diffusion.
 透光性ポリマー14に対する散乱子12の含有率は、透光性ポリマー14の種類や、散乱子12の種類や大きさによって適宜調整するので一概には特定されないが、一般的には0.1質量%以上50質量%以下であることが好ましく、0.5質量%以上15質量%以下であることがより好ましい。 The content of the scatterer 12 with respect to the translucent polymer 14 is not generally specified because it is appropriately adjusted depending on the type of the translucent polymer 14 and the type and size of the scatterer 12. The content is preferably from 50% by mass to 50% by mass, and more preferably from 0.5% by mass to 15% by mass.
 以上のように、本発明に係る光拡散層は、光を拡散する機能と光を吸収する機能とを有する。
 光拡散機能については、後述する透過型液晶表示装置の構成において(図7参照)、液晶パネルに入射する前(図7の透明保護層26に入射する前に相当する)のバックライトの輝度の角度分布と、このバックライトからの光が液晶パネルを通過し、光拡散層で拡散された後の輝度の角度分布を比較することにより評価可能である。
 より簡便には、透光性ポリマーに散乱子を添加したフィルム状試料のヘーズ(Haze、曇価)を測定することで評価できる。
As described above, the light diffusion layer according to the present invention has a function of diffusing light and a function of absorbing light.
Regarding the light diffusion function, in the configuration of the transmissive liquid crystal display device described later (see FIG. 7), the luminance of the backlight before entering the liquid crystal panel (corresponding to before entering the transparent protective layer 26 in FIG. 7) It can be evaluated by comparing the angular distribution and the angular distribution of luminance after the light from the backlight passes through the liquid crystal panel and is diffused by the light diffusion layer.
More simply, it can be evaluated by measuring the haze (Haze) of a film sample obtained by adding a scatterer to a translucent polymer.
 エッジライト式バックライトからの比較的指向性の高い光を、充分な視野角が得られるように光拡散層で広げるためには、一般的には40%以上のヘーズが必要である。しかし、必要なヘーズは、バックライトからの光の広がり度合いと光拡散層透過後に得ようとする光の広がり度合いに依存する。 In order to spread light with relatively high directivity from an edge light type backlight with a light diffusion layer so that a sufficient viewing angle can be obtained, it is generally necessary to have a haze of 40% or more. However, the required haze depends on the degree of spread of light from the backlight and the degree of spread of light to be obtained after passing through the light diffusion layer.
 例えば、非常に指向性が高く、輝度角度分布の半値全幅が30°程度以下のバックライトの光から、一般的な液晶テレビ程度の輝度角度分布の広がりを得ようとすれば、ヘーズは70%以上が望ましく、80%以上がさらに望ましい。
 また、輝度角度分布の半値全幅が30°程度以下の指向性の高いバックライトを用いる場合には、バックライト光源から発せられた光の主要波長における光拡散層の内部吸光度は、0.028以上に調整することが好適であり、0.028以上0.088以下の範囲であることがより好ましく、0.028以上0.062以下の範囲であることが更に好ましく、0.055以上0.062以下の範囲であることが、良好な黒色を表示させつつ高い正面輝度を維持する観点からは望ましい。
For example, if an attempt is made to obtain a luminance angle distribution as large as that of a general liquid crystal television from backlight light having a very high directivity and a full width at half maximum of the luminance angle distribution of about 30 ° or less, the haze is 70%. The above is desirable, and 80% or more is more desirable.
When a highly directional backlight having a full width at half maximum of the luminance angle distribution of about 30 ° or less is used, the internal absorbance of the light diffusion layer at the main wavelength of light emitted from the backlight light source is 0.028 or more. It is preferable to adjust to 0.028 or more and 0.088 or less, more preferably 0.028 or more and 0.062 or less, and 0.055 or more and 0.062 or less. The following range is desirable from the viewpoint of maintaining high front luminance while displaying good black.
 他方、より指向性が低いバックライトを用いれば、よりヘーズが低いものでも充分に拡散できる。例えば、輝度角度分布の半値全幅が30°より大きく50°以下程度の、中程度の指向性を有するバックライトの場合、ヘーズは60%以上が望ましく、70%以上がさらに望ましい。
 また、輝度角度分布の半値全幅が30°より大きく50°以下程度の中程度の指向性を有するバックライトを用いる場合には、バックライト光源から発せられた光の主要波長における光拡散層の内部吸光度は、0.020以上に調整することが好適であり、0.020以上0.095以下の範囲であることがより好ましく、0.020以上0.068以下の範囲であることが更に好ましく、0.029以上0.068以下の範囲であることが、良好な黒色を表示させつつ高い正面輝度を維持する観点からは望ましい。
On the other hand, if a backlight having lower directivity is used, even a haze having a lower haze can be sufficiently diffused. For example, in the case of a backlight having a medium directivity in which the full width at half maximum of the luminance angle distribution is greater than 30 ° and less than or equal to 50 °, the haze is desirably 60% or more, and more desirably 70% or more.
When a backlight having a medium directivity with a full width at half maximum of the luminance angle distribution of greater than 30 ° and less than or equal to 50 ° is used, the inside of the light diffusion layer at the main wavelength of light emitted from the backlight light source is used. The absorbance is preferably adjusted to 0.020 or more, more preferably 0.020 or more and 0.095 or less, and further preferably 0.020 or more and 0.068 or less. The range of 0.029 or more and 0.068 or less is desirable from the viewpoint of maintaining high front luminance while displaying good black.
 上記のように、使用するバックライトからの光の指向性によって、より好適なヘーズ値や内部吸光度の範囲は若干異なるものの、画面の白色化を抑制する観点からすれば、いずれの指向性の光であっても、光拡散層の内部吸光度を0.014以上に調整すれば効果が奏されることが後述の実施例でも示されている。 As described above, although the preferred haze value and the range of the internal absorbance are slightly different depending on the directivity of light from the backlight used, any directivity light can be used from the viewpoint of suppressing whitening of the screen. However, it is also shown in the examples described later that the effect can be obtained by adjusting the internal absorbance of the light diffusion layer to 0.014 or more.
 光を吸収する機能については、吸光度(あるいは透過率)を市販の測定機で測定することにより、評価可能である。測定には透光性ポリマーに光吸収剤を添加したフィルム状試料を用いる。そのときに光吸収剤を添加していない比較用フィルム状試料を用いてベースラインを測定することで、試料表面での反射の影響を取り除くことができる。このようにして得られたフィルム内部での吸光度を、内部吸光度と定義する。内部吸光度から減衰率および透過率が求められる。これをそれぞれ内部減衰率(%)および内部透過率(%)と定義する。内部減衰率と内部透過率を足し合わせると100%となる。 The function of absorbing light can be evaluated by measuring the absorbance (or transmittance) with a commercially available measuring instrument. For the measurement, a film sample in which a light absorbing agent is added to a translucent polymer is used. At that time, the influence of reflection on the sample surface can be removed by measuring the baseline using a comparative film-like sample to which no light absorber is added. The absorbance inside the film thus obtained is defined as internal absorbance. The attenuation rate and transmittance are determined from the internal absorbance. These are defined as internal attenuation rate (%) and internal transmittance (%), respectively. The sum of the internal attenuation and the internal transmittance is 100%.
 最終的には、上記評価結果に基づいて好適に設計した光拡散層を、図7に示すような構成の透過型液晶表示装置に設置して、その効果を評価する。 Finally, a light diffusion layer suitably designed based on the above evaluation results is installed in a transmissive liquid crystal display device having a configuration as shown in FIG. 7, and the effect is evaluated.
 光拡散層10の作製方法としては、例えば、透光性ポリマー14と散乱子12と着色剤とを含み、更に必要に応じて溶媒などを含む塗布液を調製し、この塗布液を公知の方法で透明保護層26などの液晶セルにおける最外層上に塗布する方法が挙げられる。 As a method for producing the light diffusion layer 10, for example, a coating solution containing a translucent polymer 14, a scatterer 12, and a colorant, and further containing a solvent or the like as necessary is prepared. The method of apply | coating on the outermost layer in liquid crystal cells, such as transparent protective layer 26, is mentioned.
 次に、透過型液晶表示装置について説明する。
 本発明の透過型液晶表示装置は、少なくとも、バックライト光源と、前記バックライト光源から発せられた光の指向性を制御する光制御手段と、前記光制御手段から近い側から順に、透過型の液晶セルと、透光性ポリマーと散乱子と着色剤とを含有する光拡散層と、を有する。
 本発明の透過型液晶表示装置の具体的な構成の一例を、図7を用いて説明する。
Next, a transmissive liquid crystal display device will be described.
The transmissive liquid crystal display device of the present invention comprises at least a backlight light source, a light control means for controlling the directivity of light emitted from the backlight light source, and a transmissive type in order from the side closer to the light control means. A liquid crystal cell; and a light diffusion layer containing a light-transmitting polymer, a scatterer, and a colorant.
An example of a specific configuration of the transmissive liquid crystal display device of the present invention will be described with reference to FIG.
 図7では、バックライト光源22から発せられた光が導光板24を通過して指向性を有する光となり、この光が、透明保護層26、偏光フィルム28、透明保護層26、ガラス基板30、液晶層32、カラーフィルター34、ガラス基板30、透明保護層26、偏光フィルム28、透明保護層26を通過し、光拡散層10で拡散される。 In FIG. 7, light emitted from the backlight light source 22 passes through the light guide plate 24 to become directional light, and this light is converted into a transparent protective layer 26, a polarizing film 28, a transparent protective layer 26, a glass substrate 30, It passes through the liquid crystal layer 32, the color filter 34, the glass substrate 30, the transparent protective layer 26, the polarizing film 28, and the transparent protective layer 26 and is diffused by the light diffusion layer 10.
 図7の透過型液晶表示装置では、本発明に係る液晶セルとして、透明保護層26、偏光フィルム28、透明保護層26、ガラス基板30、液晶層32、カラーフィルター34、ガラス基板30、透明保護層26、偏光フィルム28、及び透明保護層26の順に積層したものを示している。しかしこのような構成に限定されず、少なくとも液晶層32を有していればよく、各部材の使用枚数などは適宜選択でき、また、これら以外の部材を付設してもよい。 In the transmission type liquid crystal display device of FIG. 7, the liquid crystal cell according to the present invention includes a transparent protective layer 26, a polarizing film 28, a transparent protective layer 26, a glass substrate 30, a liquid crystal layer 32, a color filter 34, a glass substrate 30, and transparent protection. The layer 26, the polarizing film 28, and the transparent protective layer 26 are laminated in this order. However, the present invention is not limited to this configuration, and it is sufficient that at least the liquid crystal layer 32 is provided. The number of used members and the like can be appropriately selected, and other members may be provided.
 例えば、図7に記載の光拡散層10と隣り合う透明保護層26と光拡散層10を統合し、光拡散層を保護層として用いてもよい。透明保護層26と光拡散層10を統合し、光拡散層を保護層と兼ねて設ける場合には、該光拡散層を溶液流延製膜法、溶融押出法などの公知の製膜方法によってフィルムとして作製し、公知の方法によって偏光フィルム28に貼り合せることにより作製できる。 For example, the light diffusion layer 10 adjacent to the light diffusion layer 10 shown in FIG. 7 and the light diffusion layer 10 may be integrated, and the light diffusion layer may be used as the protection layer. When the transparent protective layer 26 and the light diffusing layer 10 are integrated and the light diffusing layer is also provided as a protective layer, the light diffusing layer is formed by a known film forming method such as a solution casting film forming method or a melt extrusion method. It can produce by producing as a film and bonding to the polarizing film 28 by a well-known method.
 また、偏光フィルム28と外側の透明保護層26とを貼り合せるための粘着剤層(図示せず)に、散乱子12および着色剤を添加し、この粘着剤層を光拡散層としてもよい。この粘着剤層には粘着性のポリマーが含まれ、該粘着性のポリマーが透光性ポリマーとして含有される。 Further, the scatterer 12 and a colorant may be added to an adhesive layer (not shown) for bonding the polarizing film 28 and the outer transparent protective layer 26, and this adhesive layer may be used as a light diffusion layer. This pressure-sensitive adhesive layer contains a pressure-sensitive polymer, and this pressure-sensitive polymer is contained as a light-transmitting polymer.
 本発明の透過型液晶表示装置に備える光拡散層10は、透光性ポリマーと散乱子と着色剤とを含有するものであればよく、図1に示す第一の態様の光拡散層、図3に示す第二の態様の光拡散層、図4に示す第三の態様の光拡散層、図5に示す第四の態様の光拡散層、更には図6に示すアンチグレア用粒子20を導入した光拡散層のいずれであってもよい。 The light diffusing layer 10 provided in the transmissive liquid crystal display device of the present invention only needs to contain a translucent polymer, a scatterer, and a colorant. The light diffusing layer of the first embodiment shown in FIG. The light diffusion layer of the second embodiment shown in FIG. 3, the light diffusion layer of the third embodiment shown in FIG. 4, the light diffusion layer of the fourth embodiment shown in FIG. 5, and the antiglare particles 20 shown in FIG. Any of the light diffusing layers may be used.
 バックライト光源22としては、冷陰極管が好適であるが、それに限定されず、熱陰極管、LEDなども使用可能である。LEDについては、白色LEDを使用してもよいし、赤、緑、青のLEDを混用し、白色を作り出してもよい。
 また、レーザーダイオードなどのレーザーをバックライト光源として用いることができる。特に偏光した光を発するレーザーは、高い効率を得ることができるため本発明の透過型液晶表示装置に好適である。レーザーダイオードはLEDと同様に、いくつかの色の光を混ぜ、白色を作り出すことが可能である。
The backlight light source 22 is preferably a cold cathode tube, but is not limited thereto, and a hot cathode tube, an LED, or the like can also be used. About LED, white LED may be used and red, green, and blue LED may be mixed and white may be produced.
Further, a laser such as a laser diode can be used as a backlight light source. In particular, a laser that emits polarized light is suitable for the transmissive liquid crystal display device of the present invention because high efficiency can be obtained. Laser diodes, like LEDs, can mix several colors of light to create a white color.
 導光板24としては公知のものを適用することができる。
 また、図7の透過型液晶表示装置では、光源部としてバックライト光源22と導光板24を備えているが、更に他の部材を付設してもよい。例えば、バックライト用の部材として一般的に用いられる、輝度を向上させるためのプリズムシート、プリズム構造を有する拡散板、光リサイクル機能を有する反射型偏光フィルム(例えば3M社のDBEFなど)等を導光板と液晶パネルの間に配置してもよい。図7では記載を省略しているが、当然のことながら、反射シート、ランプリフレクターなどの部材を導光板の周囲に配置してもよい。
A well-known thing can be applied as the light guide plate 24.
7 includes the backlight light source 22 and the light guide plate 24 as a light source unit, but other members may be additionally provided. For example, a prism sheet for improving luminance, a diffusion plate having a prism structure, a reflective polarizing film having a light recycling function (for example, 3EF DBEF), etc., which are generally used as a backlight member, are introduced. You may arrange | position between an optical board and a liquid crystal panel. Although not shown in FIG. 7, as a matter of course, members such as a reflection sheet and a lamp reflector may be arranged around the light guide plate.
 また、図7の透過型液晶表示装置では、導光板24によって指向性を有する光としているが、導光板以外の手段によって光の指向性を制御してもよい。例えば、図10に示すように、導光板の代わりに、冷陰極管を適当な間隔で配置した上に拡散板2を置き、この拡散板2の上に光を集光する機能を有するフィルムを配置したり、拡散板そのものに微細加工を施し、集光機能を持たせた拡散板を利用することも可能である。さらに、冷陰極管に代えて、LED、LDなどのより指向性の高い光を発する素子を利用した場合は、拡散シートあるいは拡散板を用いてこれらの素子から発する光の指向性を多少低めて使用することもできる。また、これらの素子に既に照明用途で用いられているような導光部品、集光部品、光反射部品を適宜組み合わせて、適度な輝度の角度分布となるように調整することも可能である。 Further, in the transmissive liquid crystal display device of FIG. 7, the light having directivity is made by the light guide plate 24, but the light directivity may be controlled by means other than the light guide plate. For example, as shown in FIG. 10, instead of the light guide plate, a film having a function of condensing light on the diffusion plate 2 is provided by placing the cold cathode tubes at appropriate intervals and placing the diffusion plate 2 thereon. It is also possible to use a diffuser plate that is arranged or finely processed on the diffuser plate itself to have a light collecting function. Furthermore, when elements that emit light with higher directivity, such as LEDs and LDs, are used in place of the cold cathode fluorescent lamps, the directivity of light emitted from these elements is slightly lowered using a diffusion sheet or a diffusion plate. It can also be used. It is also possible to adjust the angle distribution with an appropriate luminance by appropriately combining light guide parts, light collecting parts, and light reflecting parts that are already used for lighting applications in these elements.
 透過型の液晶セル(液晶層)32としては、公知の透過型の液晶セルを適用することができる。また、本発明の透過型液晶表示装置に用いる透明保護層26、偏光フィルム28、ガラス基板30、カラーフィルター34についても公知のものを適宜適用することができる。なお、本発明の透過型液晶表示装置は、本発明に係る光拡散層とともに視野角補償フィルムを用いてもよい。 As the transmissive liquid crystal cell (liquid crystal layer) 32, a known transmissive liquid crystal cell can be applied. Moreover, a well-known thing can also be applied suitably also about the transparent protective layer 26, the polarizing film 28, the glass substrate 30, and the color filter 34 which are used for the transmissive liquid crystal display device of this invention. The transmission type liquid crystal display device of the present invention may use a viewing angle compensation film together with the light diffusion layer according to the present invention.
 本発明に係る光拡散層を用いた透過型液晶表示装置は、視野角補償フィルムを用いなくとも、広い視野角を実現できる。更に、本発明に係る光拡散層を用いた透過型液晶表示装置では、コントラストの低下が抑制される。 The transmissive liquid crystal display device using the light diffusion layer according to the present invention can realize a wide viewing angle without using a viewing angle compensation film. Furthermore, in the transmissive liquid crystal display device using the light diffusion layer according to the present invention, a decrease in contrast is suppressed.
 比較的指向性の高い光を充分な視野角が得られるよう光拡散層で広げるためには、一般的には光拡散層に散乱子を多めに含有させてヘーズを高める必要がある。光拡散層が散乱子を多く含む結果、図12に示すような外光の白化が顕著に現れ、従来の光拡散層では、指向性の高いバックライトを使いこなすことが困難であった。
 しかしながら、本発明に係る光拡散層を用いれば、比較的指向性の高いバックライトを使用したときであっても、白化が抑えられつつ、充分に広い視野角が実現される。
In order to spread light with relatively high directivity in the light diffusion layer so that a sufficient viewing angle can be obtained, it is generally necessary to increase the haze by adding a large amount of scatterers to the light diffusion layer. As a result of the light diffusing layer containing many scatterers, whitening of the external light as shown in FIG. 12 appears remarkably, and it has been difficult to use a highly directional backlight with the conventional light diffusing layer.
However, when the light diffusion layer according to the present invention is used, a sufficiently wide viewing angle is realized while whitening is suppressed even when a backlight having a relatively high directivity is used.
 以下、本発明を実施例に基づいて更に詳細に説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.
[実施例1]
<光拡散層の作製>
 以下に示すような方法で、図1に示すような単層の光拡散層を作製した。
 塩化メチレン中にトリアセチルセルロースを添加し、溶解させ、均一に攪拌してポリマー溶液を調製した。この溶液を表面が平滑なステンレス基板上に塗布し、溶媒を揮発させることで、厚さ約50μmの透明保護層を作製した。
[Example 1]
<Preparation of light diffusion layer>
A single light diffusion layer as shown in FIG. 1 was produced by the method as described below.
Triacetyl cellulose was added to methylene chloride, dissolved, and stirred uniformly to prepare a polymer solution. This solution was applied on a stainless steel substrate having a smooth surface and the solvent was volatilized to produce a transparent protective layer having a thickness of about 50 μm.
 他方で、塩化メチレン中に、ポリメチルメタクリレート、赤色、青色及び黄色の有機色素を添加し、更にアルミナ微粒子(平均粒径1.1μm)を添加し、均一に攪拌して、分散液を調製した。
 なお、赤色、青色及び黄色の有機色素は、ポリメチルメタクリレートに対して下記表2の濃度(質量%)となるよう添加した。また、アルミナ微粒子は、ポリメチルメタクリレート100質量部に対し、10質量部添加した。
 前記分散液は、目的の厚さの光拡散層が得られ且つ塗布し易いよう、塩化メチレン濃度を適宜調整した。この分散液を前記透明保護層に塗布して、厚さ約30μmの光拡散層11~14を得た。
On the other hand, polymethylmethacrylate, red, blue and yellow organic dyes were added to methylene chloride, and alumina fine particles (average particle size 1.1 μm) were further added and stirred uniformly to prepare a dispersion. .
The red, blue and yellow organic dyes were added so as to have the concentrations (mass%) shown in Table 2 below with respect to polymethyl methacrylate. Moreover, 10 mass parts of alumina fine particles were added with respect to 100 mass parts of polymethyl methacrylate.
In the dispersion, the methylene chloride concentration was appropriately adjusted so that a light diffusion layer having a desired thickness was obtained and coating was easy. This dispersion was applied to the transparent protective layer to obtain light diffusion layers 11 to 14 having a thickness of about 30 μm.
<内部吸光度、内部減衰率、及び内部透過率の測定>
 内部吸光度・内部減衰率・内部透過率測定用に、上記の組成の光拡散層からアルミナ微粒子のみを取り除いた組成のフィルム(測定用試料)を作製した。
 測定用試料の作製は、まず塩化メチレン中にポリメチルメタクリレート、赤色、青色及び黄色の有機色素を添加し、均一に攪拌して溶液を調製した。この溶液を表面が平滑なステンレス基板上に塗布し、溶媒をおおよそ揮発させることで、厚さ約30μmの測定用試料11~14を作製した。なお、測定用試料11~14は、上記光拡散層11~14にそれぞれ相当する。
 測定用試料11~14のフィルムを市販の分光光度計を用いて、内部吸光度・内部減衰率・内部透過率を測定した。
<Measurement of internal absorbance, internal attenuation, and internal transmittance>
A film (measurement sample) having a composition in which only the alumina fine particles were removed from the light diffusion layer having the above composition was prepared for measuring internal absorbance, internal attenuation, and internal transmittance.
The sample for measurement was prepared by first adding polymethylmethacrylate, red, blue and yellow organic dyes into methylene chloride and stirring uniformly to prepare a solution. This solution was applied onto a stainless steel substrate having a smooth surface, and the solvent was roughly volatilized to prepare measurement samples 11 to 14 having a thickness of about 30 μm. The measurement samples 11 to 14 correspond to the light diffusion layers 11 to 14, respectively.
Internal absorbance, internal attenuation, and internal transmittance of the measurement samples 11 to 14 were measured using a commercially available spectrophotometer.
 ここで内部吸光度とは、透光性ポリマーにアルミナ粒子などの散乱子を添加せずに、光吸収物質を添加したフィルムの吸光度である。フィルム表面での反射を含めずに、フィルム内部での光吸収による吸光度を意味する。 Here, the internal absorbance is the absorbance of a film obtained by adding a light-absorbing substance without adding a scatterer such as alumina particles to a translucent polymer. It means absorbance due to light absorption inside the film without including reflection on the film surface.
 内部減衰率は、内部吸光度から換算された減衰率(%)である。
 また、内部透過率は、下記式から算出された値である。
   [内部透過率]=100(%)-[内部減衰率]
The internal attenuation rate is an attenuation rate (%) converted from the internal absorbance.
The internal transmittance is a value calculated from the following equation.
[Internal transmittance] = 100 (%)-[Internal attenuation rate]
 更に、上記組成からアルミナ微粒子および有機色素を除いた組成のポリマーフィルムを作製した。これを用いて測定した値を基準(ベースライン)とし、前述のフィルムの測定を行うことで、表面反射による損失を除いた、内部吸光度・内部減衰率・内部透過率を求めた。結果を表2に示す。 Furthermore, a polymer film having a composition obtained by removing the alumina fine particles and the organic dye from the above composition was prepared. Using the value measured using this as a reference (baseline), the above-mentioned film was measured to determine the internal absorbance, internal attenuation rate, and internal transmittance excluding the loss due to surface reflection. The results are shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
 
Figure JPOXMLDOC01-appb-T000002
 
 また、図8に、上記測定用試料11~14の内部吸光度スペクトルを示し、図9に、上記測定用試料11~14の内部透過率スペクトルを示す。 8 shows the internal absorbance spectrum of the measurement samples 11 to 14, and FIG. 9 shows the internal transmittance spectrum of the measurement samples 11 to 14.
<ヘーズの評価>
 光拡散層のヘーズ(曇価)を評価するために、有機色素を添加せずに、同一濃度のアルミナ微粒子(平均粒径1.1μm)のみを添加したポリマーフィルム(ヘーズ測定用試料)を作製した。
 ヘーズ測定用試料の作製は、まず塩化メチレン中にポリメチルメタクリレート、アルミナ微粒子を添加し、均一に攪拌して分散液を調製した。アルミナ微粒子は、ポリメチルメタクリレート100質量部に対し、10質量部添加した。この分散液を表面が平滑なステンレス基板上に塗布し、溶媒をおおよそ揮発させることで、厚さ約30μmのヘーズ測定用試料を得た。
 このヘーズ測定用試料をヘーズメーター(日本電色工業株式会社、NDH2000)で測定したところ、ヘーズは約91%であった。
<Evaluation of haze>
In order to evaluate the haze (cloudiness value) of the light diffusion layer, a polymer film (sample for haze measurement) in which only alumina fine particles having the same concentration (average particle diameter 1.1 μm) were added without adding an organic dye was prepared. did.
For the preparation of the sample for haze measurement, first, polymethyl methacrylate and alumina fine particles were added to methylene chloride, and stirred uniformly to prepare a dispersion. 10 mass parts of alumina fine particles were added with respect to 100 mass parts of polymethyl methacrylate. A sample for haze measurement having a thickness of about 30 μm was obtained by applying this dispersion onto a stainless steel substrate having a smooth surface and volatilizing the solvent.
When this haze measurement sample was measured with a haze meter (Nippon Denshoku Industries Co., Ltd., NDH2000), the haze was about 91%.
<画面の白色化の評価>
 図7の構成の透過型液晶表示素子に前記光拡散層11~14を付与して、評価を行った。液晶パネルはVA型のものを用い、バックライト光源としては主要波長が約435nm、約545nm及び約615nmの冷陰極管を用いた。また一般のリビング程度の照度である約100lxとなるように、画面の前方斜め約45度から蛍光灯で照らし、画面の白色化を評価した。評価時は画面を黒表示とした。
 その結果、内部吸光度が高い試料ほど、白色化が低減された。内部吸光度が0.014であれば実用可能であり、0.028以上であれば白色化はほとんど観られず、特に0.055以上の試料13と試料14では良好な黒が表示された。
<Evaluation of screen whitening>
The light diffusing layers 11 to 14 were applied to the transmissive liquid crystal display device having the configuration shown in FIG. 7 for evaluation. A VA type liquid crystal panel was used, and cold cathode tubes having principal wavelengths of about 435 nm, about 545 nm, and about 615 nm were used as a backlight light source. Further, the screen was illuminated with a fluorescent lamp from about 45 degrees obliquely in front of the screen so that the illuminance was about 100 lx, which was about the same level as a general living room, and the whitening of the screen was evaluated. The screen was displayed in black during the evaluation.
As a result, whitening was reduced as the sample had higher internal absorbance. If the internal absorbance is 0.014, it is practical, and if it is 0.028 or more, almost no whitening is observed. Particularly, samples 13 and 14 of 0.055 or more displayed good black.
<輝度角度分布の測定>
 上記画面の白色化の評価に用いた透過型液晶表示素子において、輝度計(株式会社トプコン、BM-7FAST)を用いて、正面輝度及び輝度角度分布を測定した。測定は画面を白表示として行った。
 液晶パネルに入射する前(図7の透明保護層26に入射前に相当する)のバックライトの輝度の角度分布は、半値全幅が約30度であった。このバックライトからの光が、液晶パネルを通過し、最前面の光拡散層で拡散された結果、光拡散層11~14のいずれにおいても半値全幅が約70度となった。
<Measurement of luminance angle distribution>
In the transmissive liquid crystal display element used for the evaluation of whitening of the screen, front luminance and luminance angle distribution were measured using a luminance meter (Topcon Corporation, BM-7FAST). The measurement was performed with the screen displayed in white.
The angular distribution of the luminance of the backlight before entering the liquid crystal panel (corresponding to before entering the transparent protective layer 26 in FIG. 7) had a full width at half maximum of about 30 degrees. The light from the backlight passed through the liquid crystal panel and was diffused by the frontmost light diffusion layer. As a result, the full width at half maximum was about 70 degrees in any of the light diffusion layers 11-14.
 比較のため、視野角補償フィルムを備える従来の液晶パネルについても正面輝度及び輝度角度分布を測定した。この視野角補償フィルムを備える従来の液晶パネルは、市販の液晶ディスプレイであり、光拡散層を有しておらず、本発明のような着色剤を添加した層も備えていない。
 視野角補償フィルムを備える従来の液晶パネルの画面は、輝度角度分布の半値全幅が約70度であることから、上記結果により、指向性の高いバックライトを使用しながらも充分な視野角を得るために必要な輝度角度分布幅を有していることが確認された。
For comparison, the front luminance and luminance angle distribution were also measured for a conventional liquid crystal panel provided with a viewing angle compensation film. A conventional liquid crystal panel provided with this viewing angle compensation film is a commercially available liquid crystal display, does not have a light diffusion layer, and does not have a layer to which a colorant as in the present invention is added.
Since the screen of a conventional liquid crystal panel provided with a viewing angle compensation film has a full width at half maximum of the luminance angle distribution of about 70 degrees, the above results provide a sufficient viewing angle while using a highly directional backlight. Therefore, it was confirmed that the brightness angle distribution width necessary for this purpose was obtained.
 なお、垂直方向の輝度角度分布についても、ほぼ同様な特性が得られた。更に、正面輝度については、表3に示すように、有機色素の添加濃度が高くなるほど低くなった。バックライト光源から発せられた光の主要波長における内部吸光度が0.062以下であれば、視野角補償フィルムを備える従来の液晶パネルの画面と同程度以上の正面輝度、輝度角度分布幅が得られている。 It should be noted that substantially the same characteristics were obtained for the luminance angle distribution in the vertical direction. Furthermore, as shown in Table 3, the front luminance decreased as the concentration of the organic dye added increased. If the internal absorbance at the main wavelength of the light emitted from the backlight light source is 0.062 or less, the front luminance and luminance angle distribution width equal to or higher than the screen of a conventional liquid crystal panel having a viewing angle compensation film can be obtained. ing.
Figure JPOXMLDOC01-appb-T000003

 
Figure JPOXMLDOC01-appb-T000003

 
 以上より、バックライト光源から発せられた光の主要波長における内部吸光度が約0.062以下の範囲の光拡散層を形成することで、図10に示すような視野角補償フィルムを備える従来の液晶パネルの画面と同程度以上の正面輝度および輝度角度分布幅を有する液晶ディスプレイが得られた。特に、バックライト光源から発せられた光の主要波長における内部吸光度が0.028~0.062の範囲の光拡散層において良好な特性が得られた。
 これらの液晶ディスプレイにおいては、光拡散層による画像の呆けはほとんど生じなかった。さらに視野角補償フィルムを用いていない構成にも関わらず、図10に示すような視野角補償フィルムを備える従来の液晶パネルの画面とほぼ同等の視野角が得られた。
As described above, a conventional liquid crystal having a viewing angle compensation film as shown in FIG. 10 is formed by forming a light diffusion layer in which the internal absorbance at a main wavelength of light emitted from a backlight light source is about 0.062 or less. A liquid crystal display having a front luminance and a luminance angle distribution width equal to or higher than the panel screen was obtained. In particular, good characteristics were obtained in a light diffusion layer having an internal absorbance in the range of 0.028 to 0.062 at the main wavelength of light emitted from a backlight light source.
In these liquid crystal displays, image blurring due to the light diffusion layer hardly occurred. Further, despite the configuration in which the viewing angle compensation film is not used, a viewing angle almost equivalent to the screen of a conventional liquid crystal panel including the viewing angle compensation film as shown in FIG. 10 was obtained.
[実施例2]
<光拡散層の作製>
 以下に示すような方法で、図4に示すような単層の光拡散層21~24を作製した。
 まず、実施例1と同様にして、透明保護層を準備した。
 一方で、塩化メチレン中に、実施例1と同様のポリメチルメタクリレート、赤色、青色及び黄色の有機色素を添加し、更にメラミン・ホルムアルデヒド縮合物微粒子(平均粒径1.3μm)を添加し、均一に攪拌して、分散液を調製した。
 なお、赤色、青色及び黄色の有機色素は、ポリメチルメタクリレートに対して下記表4の濃度(質量%)となるよう添加した。また、メラミン・ホルムアルデヒド縮合物微粒子は、ポリメチルメタクリレート100質量部に対し、5質量部添加した。
 前記分散液は、目的の厚さの光拡散層が得られ且つ塗布し易いよう、塩化メチレン濃度を適宜調整した。この分散液を前記透明保護層に塗布して、厚さ約30μmの光拡散層を得た。
[Example 2]
<Preparation of light diffusion layer>
Single-layered light diffusion layers 21 to 24 as shown in FIG. 4 were produced by the following method.
First, a transparent protective layer was prepared in the same manner as in Example 1.
On the other hand, the same polymethylmethacrylate, red, blue and yellow organic dyes as in Example 1 were added to methylene chloride, and melamine / formaldehyde condensate fine particles (average particle size 1.3 μm) were further added. And a dispersion was prepared.
The red, blue and yellow organic dyes were added so as to have the concentrations (mass%) shown in Table 4 below with respect to polymethyl methacrylate. Moreover, 5 mass parts of melamine formaldehyde condensate fine particles were added with respect to 100 mass parts of polymethyl methacrylate.
In the dispersion, the methylene chloride concentration was appropriately adjusted so that a light diffusion layer having a desired thickness was obtained and coating was easy. This dispersion was applied to the transparent protective layer to obtain a light diffusion layer having a thickness of about 30 μm.
 得られた光拡散層の断面を透過型電子顕微鏡で観察することで、添加した透光性微粒子(メラミン・ホルムアルデヒド縮合物微粒子)が、図4のように、光拡散層のなかで一方の表面側に偏って存在していることを確認した。 By observing the cross section of the obtained light diffusing layer with a transmission electron microscope, the added light transmissive fine particles (melamine / formaldehyde condensate fine particles) are on one surface in the light diffusing layer as shown in FIG. It was confirmed that it was biased to the side.
<内部吸光度、内部減衰率、及び内部透過率の測定>
 内部吸光度・内部減衰率・内部透過率測定用に、上記の組成の光拡散層からメラミン・ホルムアルデヒド縮合物微粒子のみを取り除いた組成のフィルム(測定用試料21~24)を作製した。測定用試料21~24の作製方法は、実施例1における測定用試料11~14の作製方法に準ずる。これらのフィルムを市販の分光光度計を用いて、内部吸光度・内部減衰率・内部透過率を測定した。
<Measurement of internal absorbance, internal attenuation, and internal transmittance>
For measurement of internal absorbance, internal attenuation, and internal transmittance, films (measurement samples 21 to 24) having a composition in which only melamine / formaldehyde condensate fine particles were removed from the light diffusion layer having the above composition were prepared. The production method of the measurement samples 21 to 24 is in accordance with the production method of the measurement samples 11 to 14 in Example 1. These films were measured for internal absorbance, internal attenuation, and internal transmittance using a commercially available spectrophotometer.
 また、上記組成からメラミン・ホルムアルデヒド縮合物微粒子および有機色素を除いた組成のポリマーフィルムを作製した。これを用いて測定した値を基準(ベースライン)とし、前述のフィルムの測定を行うことで、表面反射による損失を除いた、内部吸光度・内部減衰率・内部透過率を求めた。結果を表4に示す。 In addition, a polymer film having a composition obtained by removing melamine / formaldehyde condensate fine particles and organic pigment from the above composition was prepared. Using the value measured using this as a reference (baseline), the above-mentioned film was measured to determine the internal absorbance, internal attenuation rate, and internal transmittance excluding the loss due to surface reflection. The results are shown in Table 4.
Figure JPOXMLDOC01-appb-T000004
 
Figure JPOXMLDOC01-appb-T000004
 
<ヘーズの評価>
 光拡散層のヘーズを評価するために、有機色素を添加せずに、同一濃度のメラミン・ホルムアルデヒド縮合物微粒子(平均粒径1.3μm)のみを添加した、膜厚が約30μmのポリマーフィルム(ヘーズ測定用試料)を作製した。このヘーズ測定用試料の作製方法は、実施例1におけるヘーズ測定用試料の作製方法に準ずる。
 作製したヘーズ測定用試料をヘーズメーター(日本電色工業株式会社、NDH2000)で測定したところ、ヘーズは約94%であった。
<Evaluation of haze>
In order to evaluate the haze of the light diffusing layer, a polymer film having a film thickness of about 30 μm (only a melamine / formaldehyde condensate fine particle having the same concentration (average particle size 1.3 μm) is added without adding an organic dye ( Sample for haze measurement) was prepared. The method for producing the sample for haze measurement is in accordance with the method for producing the sample for haze measurement in Example 1.
When the produced haze measurement sample was measured with a haze meter (Nippon Denshoku Industries Co., Ltd., NDH2000), the haze was about 94%.
<画面の白色化の評価>
 図7の構成の透過型液晶表示素子に前記光拡散層21~24を付与して、光拡散層の評価を行った。液晶パネルはVA型のものを用い、バックライトとしては主要波長が約435nm、約545nm及び約615nmの冷陰極管を用いた。また一般のリビング程度の照度である約100lxとなるように、画面の前方斜め約45度から蛍光灯で照らし、画面の白色化を評価した。評価時は、画面を黒表示とした。
 その結果、内部吸光度が高い試料ほど、白色化が低減された。バックライト光源から発せられた光の主要波長における内部吸光度が0.014であれば実用可能であり、0.028以上であれば白色化はほとんど観られず、特に、バックライト光源から発せられた光の主要波長における内部吸光度が0.055以上の試料23と試料24では良好な黒が表示された。
<Evaluation of screen whitening>
The light diffusing layers 21 to 24 were added to the transmissive liquid crystal display element having the configuration shown in FIG. 7 to evaluate the light diffusing layers. The liquid crystal panel was a VA type, and a cold cathode tube having principal wavelengths of about 435 nm, about 545 nm, and about 615 nm was used as the backlight. Further, the screen was illuminated with a fluorescent lamp from about 45 degrees obliquely in front of the screen so that the illuminance was about 100 lx, which was about the same level as a general living room, and the whitening of the screen was evaluated. At the time of evaluation, the screen was displayed in black.
As a result, whitening was reduced as the sample had higher internal absorbance. If the internal absorbance at the main wavelength of the light emitted from the backlight light source is 0.014, it is practical, and if it is 0.028 or more, whitening is hardly observed, and in particular, it is emitted from the backlight light source. Good black was displayed for Sample 23 and Sample 24 having an internal absorbance of 0.055 or more at the main wavelength of light.
<輝度角度分布の測定>
 上記画面の白色化の評価に用いた透過型液晶表示素子において、輝度計(株式会社トプコン、BM-7FAST)を用いて、正面輝度及び輝度角度分布を測定した。測定は画面を白表示として行った。
 液晶パネルに入射する前(図7の透明保護層26に入射前に相当する)のバックライトの輝度の角度分布は、半値全幅が約30度であった。このバックライトからの光が、液晶パネルを通過し、最前面の光拡散層で拡散された結果、光散乱層21~24のいずれにおいても半値全幅が約70度となった。
<Measurement of luminance angle distribution>
In the transmissive liquid crystal display element used for the evaluation of whitening of the screen, front luminance and luminance angle distribution were measured using a luminance meter (Topcon Corporation, BM-7FAST). The measurement was performed with the screen displayed in white.
The angular distribution of the luminance of the backlight before entering the liquid crystal panel (corresponding to before entering the transparent protective layer 26 in FIG. 7) had a full width at half maximum of about 30 degrees. The light from the backlight passed through the liquid crystal panel and was diffused by the frontmost light diffusion layer. As a result, the full width at half maximum was about 70 degrees in any of the light scattering layers 21 to 24.
 視野角補償フィルムを備える従来の液晶パネルの画面は、輝度角度分布の半値全幅が約70度であることから、上記結果により、指向性の高いバックライトを使用しながらも充分な視野角を得るために必要な輝度角度分布幅を有していることが確認された。 Since the screen of a conventional liquid crystal panel provided with a viewing angle compensation film has a full width at half maximum of the luminance angle distribution of about 70 degrees, the above results provide a sufficient viewing angle while using a highly directional backlight. Therefore, it was confirmed that the brightness angle distribution width necessary for this purpose was obtained.
 なお、垂直方向の輝度角度分布についても、ほぼ同様な特性が得られた。更に、正面輝度については、表5に示すように、有機色素の添加濃度が高くなるほど低くなった。バックライト光源から発せられた光の主要波長における内部吸光度が0.062以下であれば、視野角補償フィルムを備える従来の液晶パネルの画面と同程度以上の正面輝度、輝度角度分布幅が得られている。 It should be noted that substantially the same characteristics were obtained for the luminance angle distribution in the vertical direction. Furthermore, as shown in Table 5, the front luminance decreased as the concentration of the organic dye added increased. If the internal absorbance at the main wavelength of the light emitted from the backlight light source is 0.062 or less, the front luminance and luminance angle distribution width equal to or higher than the screen of a conventional liquid crystal panel having a viewing angle compensation film can be obtained. ing.
Figure JPOXMLDOC01-appb-T000005

 
Figure JPOXMLDOC01-appb-T000005

 
[実施例3]
 以下に示すような方法で、図5に示すような積層の光拡散層、つまり透光性ポリマーに散乱子を添加した散乱層16の外側(観察者側)に、透光性ポリマーに着色剤を添加した着色層18を積層したものを作製した。透光性ポリマーとして、トリアセチルセルロースを選択した。
[Example 3]
In the method shown below, the light-transmitting polymer has a colorant on the outer side (observer side) of the light-diffusing layer having the laminated structure as shown in FIG. A layer in which a colored layer 18 to which is added was laminated was produced. Triacetyl cellulose was selected as the translucent polymer.
<光拡散層の作製>
 まず、トリアセチルセルロースを塩化メチレンに溶解し、さらにアルミナ微粒子(平均粒径1.1μm)を添加し、均一に攪拌し、分散液-1を調製した。アルミナ微粒子は、トリアセチルセルロース100質量部に対し、10質量部添加した。分散液-1は、目的の膜厚が得られ且つ塗布し易いよう、塩化メチレン濃度を適宜調整した。
 他方、トリアセチルセルロースと赤色、青色、黄色の有機色素を塩化メチレンに溶解し、均一に攪拌し、溶液-1を調製した。赤色、青色及び黄色の有機色素は、トリアセチルセルロースに対して下記表6の濃度(質量%)となるよう添加した。溶液-1は、目的の膜厚が得られ且つ塗布し易いよう、塩化メチレン濃度を適宜調整した。
<Preparation of light diffusion layer>
First, triacetyl cellulose was dissolved in methylene chloride, alumina fine particles (average particle size 1.1 μm) were added, and the mixture was stirred uniformly to prepare Dispersion-1. 10 mass parts of alumina fine particles were added with respect to 100 mass parts of triacetyl cellulose. In Dispersion-1, the methylene chloride concentration was appropriately adjusted so that the desired film thickness was obtained and coating was easy.
On the other hand, triacetyl cellulose and red, blue, and yellow organic dyes were dissolved in methylene chloride and stirred uniformly to prepare Solution-1. The red, blue and yellow organic dyes were added so as to have the concentrations (mass%) shown in Table 6 below with respect to triacetylcellulose. In Solution-1, the methylene chloride concentration was appropriately adjusted so that the desired film thickness was obtained and coating was easy.
 実施例1と同様の方法で準備した透明保護層に、前記分散液-1を塗布し、厚さ約30μmの散乱層16を得た。さらに散乱層16の上に前記溶液-1を塗布し、厚さ約30μmの着色層18を形成し、光拡散層31~34を得た。 The dispersion liquid-1 was applied to the transparent protective layer prepared in the same manner as in Example 1 to obtain a scattering layer 16 having a thickness of about 30 μm. Further, the solution-1 was applied on the scattering layer 16 to form a colored layer 18 having a thickness of about 30 μm, and light diffusion layers 31 to 34 were obtained.
<内部吸光度・内部減衰率及び内部透過率の測定>
 内部吸光度・内部減衰率・内部透過率の測定用に、着色層18と同等の組成のフィルム(測定用試料31~34)を作製した。この測定用試料31~34の作製方法は、実施例1における測定用試料11~14の作製方法に準ずる。フィルム厚さは約30μmとした。これらのフィルムを市販の分光光度計を用いて、内部吸光度・内部減衰率・内部透過率を測定した。
<Measurement of internal absorbance, internal attenuation, and internal transmittance>
Films (measuring samples 31 to 34) having the same composition as the colored layer 18 were prepared for measuring the internal absorbance, the internal attenuation rate, and the internal transmittance. The method for producing the measurement samples 31 to 34 is in accordance with the method for producing the measurement samples 11 to 14 in Example 1. The film thickness was about 30 μm. These films were measured for internal absorbance, internal attenuation, and internal transmittance using a commercially available spectrophotometer.
 また色素を添加せずにポリマーのみのフィルムを作製した。これを用いて測定した値を基準(ベースライン)とし、前述のフィルムの測定を行うことで、表面反射による損失を除いた、内部吸光度・内部透過率を求めた。結果を表6に示す。 Also, a polymer-only film was prepared without adding a dye. Using the value measured using this as a reference (baseline), the above-mentioned film was measured to determine the internal absorbance and internal transmittance excluding the loss due to surface reflection. The results are shown in Table 6.
Figure JPOXMLDOC01-appb-T000006

 
Figure JPOXMLDOC01-appb-T000006

 
<ヘーズの評価>
 光拡散層のヘーズを評価するために、上記実施例3の散乱層16と同等の組成のフィルム(ヘーズ測定用試料)を作製した。このヘーズ測定用試料の作製方法は、実施例1におけるヘーズ測定用試料の作製方法に準ずる。
 作製したヘーズ測定用試料をヘーズメーター(日本電色工業株式会社、NDH2000)で測定したところ、ヘーズは約92%であった。
<Evaluation of haze>
In order to evaluate the haze of the light diffusion layer, a film (haze measurement sample) having the same composition as that of the scattering layer 16 of Example 3 was prepared. The method for producing the sample for haze measurement is in accordance with the method for producing the sample for haze measurement in Example 1.
When the produced haze measurement sample was measured with a haze meter (Nippon Denshoku Industries Co., Ltd., NDH2000), the haze was about 92%.
<画面の白色化の評価>
 図7の構成の透過型液晶表示素子に前記光散乱層31~34を付与して、光拡散層の評価を行った。液晶パネルはVA型のものを用い、バックライトとしては主要波長が約435nm、約545nm及び約615nmの冷陰極管を用いた。また一般のリビング程度の照度である約100lxとなるように、画面の前方斜め約45度から蛍光灯で照らし、画面の白色化を評価した。評価時は、画面を黒表示とした。
 その結果、内部吸光度が高い試料ほど、白色化が低減された。バックライト光源から発せられた光の主要波長における内部吸光度が0.014であれば実用可能であり、0.029以上であれば白色化はほとんど観られず、特にバックライト光源から発せられた光の主要波長における内部吸光度が0.056以上の試料33と試料34では良好な黒が表示された。
<Evaluation of screen whitening>
The light scattering layers 31 to 34 were applied to the transmissive liquid crystal display element having the configuration shown in FIG. 7 to evaluate the light diffusion layer. The liquid crystal panel was a VA type, and a cold cathode tube having principal wavelengths of about 435 nm, about 545 nm, and about 615 nm was used as the backlight. Further, the screen was illuminated with a fluorescent lamp from about 45 degrees obliquely in front of the screen so that the illuminance was about 100 lx, which was about the same level as a general living room, and the whitening of the screen was evaluated. At the time of evaluation, the screen was displayed in black.
As a result, whitening was reduced as the sample had higher internal absorbance. If the internal absorbance at the main wavelength of light emitted from the backlight source is 0.014, it is practical, and if it is 0.029 or more, almost no whitening is observed, especially light emitted from the backlight source. Samples 33 and 34 having an internal absorbance of 0.056 or more at the main wavelength indicated good black.
<輝度角度分布の測定>
 上記画面の白色化の評価に用いた透過型液晶表示素子において、輝度計(株式会社トプコン、BM-7FAST)を用いて、正面輝度および輝度の水平方向の角度分布を測定した。測定は画面を白表示として行った。使用したバックライトの液晶パネルに入射する前(図7の透明保護層26に入射前に相当)の輝度の角度分布は、半値全幅が約30度であった。このバックライトからの光が、液晶パネルを通過し、最前面の光拡散層で拡散された結果、いずれの光拡散層においても半値全幅が約70度となった。
<Measurement of luminance angle distribution>
In the transmissive liquid crystal display element used for the evaluation of the whitening of the screen, the luminance distribution (Topcon Co., Ltd., BM-7FAST) was used to measure the front luminance and the angular distribution of luminance in the horizontal direction. The measurement was performed with the screen displayed in white. The angular distribution of the luminance before entering the liquid crystal panel of the backlight used (equivalent to before entering the transparent protective layer 26 in FIG. 7) had a full width at half maximum of about 30 degrees. The light from the backlight passed through the liquid crystal panel and was diffused by the frontmost light diffusion layer. As a result, the full width at half maximum was about 70 degrees in any of the light diffusion layers.
 視野角補償フィルムを備える従来の液晶パネルの画面は、輝度角度分布の半値全幅が約70度であったことから、指向性の高いバックライトを使用しながらも、充分な視野角を得るために必要な輝度の角度分布幅を有していることが確認された。 The screen of a conventional liquid crystal panel equipped with a viewing angle compensation film has a full width at half maximum of the luminance angle distribution of about 70 degrees, so that a sufficient viewing angle can be obtained while using a highly directional backlight. It was confirmed that it had the necessary angular distribution width of luminance.
 正面輝度については、表7に示すように、有機色素の添加濃度が高くなるほど低くなった。バックライト光源から発せられた光の主要波長における内部吸光度が0.062以下であれば、視野角補償フィルムを備える従来の液晶パネルの画面と同程度以上の正面輝度、輝度角度分布幅が得られている。 As shown in Table 7, the front luminance was lower as the concentration of the organic dye added was higher. If the internal absorbance at the main wavelength of the light emitted from the backlight light source is 0.062 or less, the front luminance and luminance angle distribution width equal to or higher than the screen of a conventional liquid crystal panel having a viewing angle compensation film can be obtained. ing.
Figure JPOXMLDOC01-appb-T000007

 
Figure JPOXMLDOC01-appb-T000007

 
 以上、実施例1~3により、視野角補償フィルムを用いていない構成にも関わらず、図10に示すような視野角補償フィルムを備える従来の液晶パネルの画面とほぼ同等の視野角が得られた。
 また、実施例1~3により、バックライト光源から発せられた光の主要波長における内部吸光度が約0.062以下の範囲に相当する光拡散層を形成することで、白色化が良好に低減され、図10に示すような視野角補償フィルムを備える従来の液晶パネルの画面と同程度以上の正面輝度および輝度角度分布幅を有する液晶ディスプレイを得ることができた。特に、バックライト光源から発せられた光の主要波長における内部吸光度が0.028~0.062の範囲においては良好な特性が得られた。
 更に、実施例1~3の光拡散層を備える液晶ディスプレイにおいては、光拡散層による画像の呆けはほとんど生じなかった。
As described above, according to Examples 1 to 3, a viewing angle almost equivalent to the screen of a conventional liquid crystal panel including the viewing angle compensation film as shown in FIG. 10 can be obtained regardless of the configuration in which the viewing angle compensation film is not used. It was.
Further, according to Examples 1 to 3, by forming a light diffusion layer corresponding to a range in which the internal absorbance at the main wavelength of the light emitted from the backlight light source is about 0.062 or less, whitening is favorably reduced. A liquid crystal display having a front luminance and a luminance angle distribution width comparable to or higher than that of a screen of a conventional liquid crystal panel provided with a viewing angle compensation film as shown in FIG. 10 could be obtained. In particular, good characteristics were obtained when the internal absorbance at the main wavelength of light emitted from the backlight source was in the range of 0.028 to 0.062.
Further, in the liquid crystal displays provided with the light diffusion layers of Examples 1 to 3, image blurring due to the light diffusion layer hardly occurred.
 なお、従来、透過型液晶表示装置の光拡散層に着色剤を添加することは行なわれていなかった。これは、そもそも外光によるコントラスト低下の防止に着色剤を利用するということが想定されていなかったことにもよるが、バックライトからの光を着色剤が吸収して著しい輝度の低下を招くとの懸念が存在していた可能性があり、敢えて積極的に着色剤を添加する理由がなかったものと推測される。しかしながら、実施例1~3の結果に示されるように、着色剤を添加しても従来の液晶表示装置と同程度以上の輝度が呈される上、外光によるコントラストの低下が抑えられる。 Conventionally, a colorant has not been added to the light diffusion layer of the transmissive liquid crystal display device. This is due to the fact that it was not assumed that a colorant was used to prevent a decrease in contrast due to external light, but the colorant absorbed the light from the backlight and caused a significant decrease in brightness. It is speculated that there was no reason to positively add colorants. However, as shown in the results of Examples 1 to 3, even when a colorant is added, brightness equal to or higher than that of a conventional liquid crystal display device is exhibited, and a decrease in contrast due to external light can be suppressed.
[実施例4]
<光拡散層の作製> 
 以下に示すような方法で、光拡散層41~45を作製した。
 まず、実施例1と同様にして、透明保護層を準備した。
 一方で、酢酸エチル中にポリメチルメタクリレート、赤色、青色及び黄色の有機顔料として、それぞれC.I.Pigment Red 48:3(山陽色素株式会社)、C.I.Pigment Blue 15:1(銅化合物)(山陽色素株式会社)、C.I.Pigment Yellow 14(山陽色素株式会社)を添加し、更にアルミナ微粒子(平均粒径1.1μm)を添加し、均一に撹拌して、分散液を調製した。
 なお、赤色、青色及び黄色の有機顔料は、ポリメチルメタクリレートに対して下記表8の濃度(質量%)となるように添加した。また、アルミナ微粒子は、ポリメチルメタクリレート100質量部に対して5質量部となるよう添加した。
 前記分散液は、目的の厚さの光拡散層が得られ且つ塗布し易いよう、酢酸エチル濃度を適宜調製した。この分散液を前記透明保護層に塗布して、厚さ約30μmの光拡散層41~45を得た。
[Example 4]
<Preparation of light diffusion layer>
The light diffusion layers 41 to 45 were produced by the method as described below.
First, a transparent protective layer was prepared in the same manner as in Example 1.
On the other hand, as polymethyl methacrylate, red, blue and yellow organic pigments in ethyl acetate, CIPigment Red 48: 3 (Sanyo Dye Co., Ltd.), CIPigment Blue 15: 1 (Copper Compound) (Sanyo Dye Co., Ltd.), CIPigment Yellow 14 (Sanyo Dyeing Co., Ltd.) was added, alumina fine particles (average particle size 1.1 μm) were further added, and stirred uniformly to prepare a dispersion.
The red, blue and yellow organic pigments were added so as to have the concentration (mass%) shown in Table 8 below with respect to polymethyl methacrylate. The alumina fine particles were added so as to be 5 parts by mass with respect to 100 parts by mass of polymethyl methacrylate.
The dispersion was appropriately adjusted in ethyl acetate concentration so that a light diffusion layer having a desired thickness was obtained and coating was easy. This dispersion was applied to the transparent protective layer to obtain light diffusion layers 41 to 45 having a thickness of about 30 μm.
<内部吸光度・内部減衰率及び内部透過率の測定>
 内部吸光度・内部減衰率・内部透過率測定用に、上記の組成の光拡散層からアルミナ微粒子のみを取り除いた組成のフィルム(測定用試料41~45)を作製した。測定用試料41~45の作製方法は、実施例1における測定用試料11~14の作製方法に準ずる。これらのフィルムを市販の分光光度計を用いて、内部吸光度・内部減衰率・内部透過率を測定した。
<Measurement of internal absorbance, internal attenuation, and internal transmittance>
Films (measurement samples 41 to 45) having a composition in which only the alumina fine particles were removed from the light diffusion layer having the above composition were prepared for measuring internal absorbance, internal attenuation, and internal transmittance. The production method of the measurement samples 41 to 45 is in accordance with the production method of the measurement samples 11 to 14 in Example 1. These films were measured for internal absorbance, internal attenuation, and internal transmittance using a commercially available spectrophotometer.
 また、上記組成からアルミナ微粒子および有機色素を除いた組成のポリマーフィルムを作製した。これを用いて測定した値を基準(ベースライン)とし、前述のフィルムの測定を行うことで、表面反射による損失を除いた、内部吸光度・内部減衰率・内部透過率を求めた。結果を表8に示す。 Further, a polymer film having a composition obtained by removing the alumina fine particles and the organic dye from the above composition was prepared. Using the value measured using this as a reference (baseline), the above-mentioned film was measured to determine the internal absorbance, internal attenuation rate, and internal transmittance excluding the loss due to surface reflection. The results are shown in Table 8.
Figure JPOXMLDOC01-appb-T000008
 
Figure JPOXMLDOC01-appb-T000008
 
<ヘーズの評価> 
 光拡散層のヘーズを評価するために、有機色素を添加せずに、同一濃度のアルミナ微粒子(平均粒径1.1μm)のみを添加した、膜厚が約30μmのポリマーフィルム(ヘーズ測定用試料)を作製した。このヘーズ測定用試料の作製方法は、実施例1におけるヘーズ測定用試料の作製方法に準ずる。
 作製したヘーズ測定用試料をヘーズメーター(日本電色工業株式会社、NDH2000)で測定したところ、ヘーズは約77%であった。
<Evaluation of haze>
In order to evaluate the haze of the light diffusing layer, a polymer film having a film thickness of about 30 μm (sample for haze measurement) in which only the alumina fine particles having the same concentration (average particle diameter 1.1 μm) are added without adding an organic dye. ) Was produced. The method for producing the sample for haze measurement is in accordance with the method for producing the sample for haze measurement in Example 1.
When the produced haze measurement sample was measured with a haze meter (Nippon Denshoku Industries Co., Ltd., NDH2000), the haze was about 77%.
<画面の白色化の評価> 
 図7の構成の透過型液晶表示素子に前記光散乱層41~45を付与して、光拡散層の評価を行った。液晶パネルはIPS型のものを用い、バックライトとしては主要波長が約435nm、約545nm及び約615nmの冷陰極管を用いた。また一般リビング程度の照度である約100lxとなるように、画面前方斜め45度から蛍光灯で照らし、画面の白色化を評価した。評価時は、画面を黒表示した。
 その結果、内部吸光度が高い試料ほど、白色化が低減された。バックライト光源から発せられた光の主要波長における内部吸光度が0.014であれば実用可能であり、0.020以上であれば、白色化はほとんど観られず、特に、バックライト光源から発せられた光の主要波長における内部吸光度が0.029以上の試料43~試料45では良好な黒が表示された。
<Evaluation of screen whitening>
The light scattering layers 41 to 45 were added to the transmissive liquid crystal display element having the configuration shown in FIG. 7 to evaluate the light diffusion layer. An IPS type liquid crystal panel was used, and cold cathode tubes having principal wavelengths of about 435 nm, about 545 nm, and about 615 nm were used as the backlight. In addition, the screen was illuminated with a fluorescent lamp from 45 degrees obliquely in front of the screen to evaluate the whitening of the screen so that the illuminance is about 100 lx, which is about the same level as a general living room. During the evaluation, the screen was displayed in black.
As a result, whitening was reduced as the sample had higher internal absorbance. If the internal absorbance at the main wavelength of the light emitted from the backlight source is 0.014, it is practical, and if it is 0.020 or more, almost no whitening is observed, and in particular, it is emitted from the backlight source. Samples 43 to 45 having an internal absorbance of 0.029 or more at the main wavelength of light displayed good black.
<輝度角度分布の測定> 
 上記画面の白色化の評価に用いた透過型液晶表示素子において、実施例1と同様にして、輝度角度分布を測定した。なお、輝度角分布の測定に使用した光拡散層としての輝度角分布測定用試料41及び42は、上記表8の試料43に示す量の有機顔料を添加し、アルミナ微粒子をポリメチルメタクリレート100質量部に対して5質量部または10質量部となるよう添加したものである。
 使用したバックライトの液晶パネルに入射する前(図7の透明保護層26に入射前に相当する)の輝度角度分布は、半値全幅が約47度であった。このバックライトからの光が、液晶パネルを通過し、最前面の光拡散層で拡散された結果、表9に示すように、いずれの光拡散層においても半値全幅が約70度以上となった。
<Measurement of luminance angle distribution>
In the transmissive liquid crystal display element used for the evaluation of the whitening of the screen, the luminance angle distribution was measured in the same manner as in Example 1. The luminance angle distribution measurement samples 41 and 42 as the light diffusion layer used for the measurement of the luminance angle distribution were added with an organic pigment in the amount shown in the sample 43 of Table 8 above, and the alumina fine particles were added to 100 mass of polymethyl methacrylate. It is added so that it may become 5 mass parts or 10 mass parts with respect to a part.
The luminance angle distribution before entering the liquid crystal panel of the backlight used (corresponding to before entering the transparent protective layer 26 in FIG. 7) had a full width at half maximum of about 47 degrees. As a result of the light from this backlight passing through the liquid crystal panel and being diffused by the frontmost light diffusion layer, as shown in Table 9, the full width at half maximum was about 70 degrees or more in any of the light diffusion layers. .
Figure JPOXMLDOC01-appb-T000009
 
Figure JPOXMLDOC01-appb-T000009
 
 視野角補償フィルムを備える従来の液晶パネルの画面は、輝度角度分布の半値全幅が約70度であったことから、輝度角度分布の半値全幅が47度のバックライトを使用した場合には、輝度角分布測定用試料41において、十分な視野角を得るために必要な輝度の角度分布幅を有していることが確認された。 Since the screen of the conventional liquid crystal panel provided with the viewing angle compensation film has a full width at half maximum of the luminance angle distribution of about 70 degrees, when a backlight having a full width at half maximum of the luminance angle distribution of 47 degrees is used, the luminance It was confirmed that the angular distribution measurement sample 41 has an angular distribution width of luminance necessary for obtaining a sufficient viewing angle.
 実施例4により、輝度角度分布における半値全幅が約47度のバックライトを使用した場合には、バックライト光源から発せられた光の主要波長における内部吸光度が約0.020以上の範囲に相当する光拡散層を形成することで、白色化が良好に低減され、且つ充分に視野角が広がり輝度の半値全幅が約70度以上となった。特に、バックライト光源から発せられた光の主要波長における内部吸光度が0.029以上の範囲においては良好な特性が得られた。
 更に、実施例4の光拡散層を備える液晶ディスプレイにおいては、光拡散層による画像の呆けはほとんど生じなかった。
According to Example 4, when a backlight having a full width at half maximum of about 47 degrees in the luminance angle distribution is used, the internal absorbance at the main wavelength of the light emitted from the backlight source corresponds to a range of about 0.020 or more. By forming the light diffusion layer, whitening was satisfactorily reduced, the viewing angle was sufficiently widened, and the full width at half maximum of luminance was about 70 degrees or more. In particular, good characteristics were obtained when the internal absorbance at the main wavelength of light emitted from the backlight source was 0.029 or more.
Further, in the liquid crystal display having the light diffusion layer of Example 4, image blurring due to the light diffusion layer hardly occurred.
[実施例5]
<保護層を兼ねた光拡散層の作製>
 以下に示すような方法で、保護層を兼ねた光拡散層51を作製した。
 酢酸エチル中に、実施例4と同様のポリメチルメタクリレートおよび赤色、青色、黄色の有機顔料を添加し、更におよびアルミナ微粒子(平均粒径1.1μm)を添加し、均一に撹拌して、分散液を調製した。
 なお、アルミナ微粒子は、ポリメチルメタクリレート100質量部に対して20質量部となるよう添加した。また、赤色、青色及び黄色の有機顔料としては、それぞれC.I.Pigment Red 48:3(山陽色素株式会社)、C.I.Pigment Blue 15:1(銅化合物)(山陽色素株式会社)、C.I.Pigment Yellow 14(山陽色素株式会社)を使用した。赤色、青色及び黄色の有機顔料は、ポリメチルメタクリレート100質量部に対して、それぞれ0.392質量部、0.072質量部、0.120質量部となるように添加した。 
[Example 5]
<Preparation of a light diffusion layer that also serves as a protective layer>
A light diffusion layer 51 that also serves as a protective layer was produced by the method described below.
The same polymethylmethacrylate and red, blue and yellow organic pigments as in Example 4 were added to ethyl acetate, and alumina fine particles (average particle size 1.1 μm) were further added, and the mixture was stirred and dispersed uniformly. A liquid was prepared.
The alumina fine particles were added so as to be 20 parts by mass with respect to 100 parts by mass of polymethyl methacrylate. Moreover, as red, blue and yellow organic pigments, CIPigment Red 48: 3 (Sanyo Dye Co., Ltd.), CIPigment Blue 15: 1 (Copper Compound) (Sanyo Dye Co., Ltd.), CIPigment Yellow 14 (Sanyo Dye Co., Ltd.) )It was used. The red, blue, and yellow organic pigments were added to 0.392 parts by mass, 0.072 parts by mass, and 0.120 parts by mass, respectively, with respect to 100 parts by mass of polymethyl methacrylate.
 この分散液を表面が平滑なステンレス基板上に塗布し、溶媒をおおよそ乾燥させることによりフィルム状試料を作製し、得られたフィルム状試料を粉砕し、さらに減圧下で乾燥させた。得られた試料を、3倍量のポリメチルメタクリレートのペレットと混ぜ、230℃で2軸押出機を用いて混練後、270℃で単軸押出機を用いてフィルム状に押出成形を行い、ロールで巻き取った。以上のようにして、保護層を兼ねた光拡散層51を作製した。 The dispersion was applied on a stainless steel substrate having a smooth surface, and the solvent was roughly dried to prepare a film sample. The obtained film sample was pulverized and further dried under reduced pressure. The obtained sample was mixed with 3 times the amount of polymethylmethacrylate pellets, kneaded using a twin screw extruder at 230 ° C., and then extruded into a film using a single screw extruder at 270 ° C. I wound up with. As described above, the light diffusion layer 51 also serving as the protective layer was produced.
 実施例5の保護層を兼ねた光拡散層51は、実施例4の光拡散層42と有機色素濃度及びアルミナ微粒子の添加量がそれぞれ同一であることから、実施例4の光拡散層42と同様の効果が奏されるものと考えられる。 The light diffusing layer 51 that also serves as the protective layer of Example 5 is the same as the light diffusing layer 42 of Example 4 in the organic dye concentration and the addition amount of the alumina fine particles. It is thought that the same effect is produced.
[実施例6]
<粘着剤層を兼ねた光拡散層の作製>
 以下に示すような方法で、粘着剤層を兼ねた光拡散層61を作製した。
 ブチルアクリレート:アクリル酸:2-ヒドロキシエチルアクリレート=100:5:0.1(重量比)の共重合体からなる重量平均分子量10万程度のアクリル系ポリマーを酢酸エチルに溶解させ、共重合体の濃度が約30質量%の溶液を調整した。上記アクリル系ポリマー溶液にイソシアネート系多官能性化合物である日本ポリウレタン社製コロネートLをポリマー固形分100質量部に対して4質量部、および添加剤(KBM403、信越化学工業株式会社製)を0.5質量部、アルミナ微粒子(平均粒径1.1μm)を5質量部および赤色、青色、黄色の有機顔料を添加し、粘着剤溶液を調製した。
 赤色、青色及び黄色の有機顔料としては、それぞれC.I.Pigment Red 48:3(山陽色素株式会社)、C.I.Pigment Blue 15:1(銅化合物)(山陽色素株式会社)、C.I.Pigment Yellow 14(山陽色素株式会社)を使用した。なお、赤色、青色及び黄色の有機顔料は、上記共重合体100質量部に対してそれぞれ0.098質量部、0.018質量部、0.030質量部となるように添加した。
[Example 6]
<Preparation of a light diffusion layer that also serves as an adhesive layer>
A light diffusion layer 61 that also serves as a pressure-sensitive adhesive layer was produced by the method described below.
An acrylic polymer having a weight average molecular weight of about 100,000 consisting of a copolymer of butyl acrylate: acrylic acid: 2-hydroxyethyl acrylate = 100: 5: 0.1 (weight ratio) is dissolved in ethyl acetate. A solution having a concentration of about 30% by mass was prepared. Coronate L manufactured by Nippon Polyurethane Co., Ltd., which is an isocyanate-based polyfunctional compound, is added to the acrylic polymer solution in an amount of 4 parts by mass with respect to 100 parts by mass of polymer solids, and additives (KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) 5 parts by mass, 5 parts by mass of alumina fine particles (average particle size 1.1 μm), and red, blue and yellow organic pigments were added to prepare an adhesive solution.
As red, blue and yellow organic pigments, CIPigment Red 48: 3 (Sanyo Dye Co., Ltd.), CIPigment Blue 15: 1 (Copper Compound) (Sanyo Dye Co., Ltd.), CIPigment Yellow 14 (Sanyo Dye Co., Ltd.) used. The red, blue and yellow organic pigments were added to 0.098 parts by mass, 0.018 parts by mass and 0.030 parts by mass with respect to 100 parts by mass of the copolymer.
 粘度調整のための溶剤(酢酸エチル)を加え、当該粘着剤溶液を、乾燥後の厚みが25μmとなるように、離型フィルム(ポリエチレンテレフタレート基材:ダイヤホイルMRF38、三菱化学ポリエステル製)上に塗布した後、熱風循環式オーブンで乾燥して、散乱子および着色剤を含んだ粘着剤層を形成した。この粘着剤層を用いて偏光フィルム28と外側の透明保護層26とを貼り合せた。 A solvent for adjusting viscosity (ethyl acetate) is added, and the pressure-sensitive adhesive solution is placed on a release film (polyethylene terephthalate substrate: Diafoil MRF38, manufactured by Mitsubishi Chemical Polyester) so that the thickness after drying is 25 μm. After the application, it was dried in a hot air circulation oven to form an adhesive layer containing a scatterer and a colorant. The polarizing film 28 and the outer transparent protective layer 26 were bonded together using this pressure-sensitive adhesive layer.
 実施例6の粘着層を兼ねた光拡散層61は、実施例4の光拡散層42と有機色素濃度及びアルミナ微粒子の添加量がそれぞれ同一であることから、実施例4の光拡散層42と同様の効果が奏されるものと考えられる。 The light diffusing layer 61 that also serves as the adhesive layer of Example 6 is the same as the light diffusing layer 42 of Example 4 in the organic dye concentration and the addition amount of the alumina fine particles. It is thought that the same effect is produced.
 2009年6月9日に出願された日本国特許出願2009-138442の開示はその全体が参照により本明細書に取り込まれる。
 本明細書に記載された全ての文献、特許出願、および技術規格は、個々の文献、特許出願、および技術規格が参照により取り込まれることが具体的かつ個々に記された場合と同程度に、本明細書中に参照により取り込まれる。
The disclosure of Japanese Patent Application No. 2009-138442 filed on June 9, 2009 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually described to be incorporated by reference, Incorporated herein by reference.

Claims (6)

  1.  少なくとも、
     バックライト光源と、
     前記バックライト光源から発せられた光の指向性を制御する光制御手段と、
     前記光制御手段から近い側から順に、透過型の液晶セルと、透光性ポリマーと散乱子と着色剤とを含有する光拡散層と、
    を有する透過型液晶表示装置。
    at least,
    A backlight light source;
    Light control means for controlling the directivity of light emitted from the backlight light source;
    In order from the side closer to the light control means, a transmissive liquid crystal cell, a light diffusing layer containing a translucent polymer, a scatterer, and a colorant,
    A transmissive liquid crystal display device.
  2.  前記光拡散層は、前記バックライト光源から発せられた光の主要波長における内部吸光度が0.014以上である請求項1に記載の透過型液晶表示装置。 The transmissive liquid crystal display device according to claim 1, wherein the light diffusion layer has an internal absorbance of 0.014 or more at a main wavelength of light emitted from the backlight light source.
  3.  前記光拡散層は、前記バックライト光源から発せられた光の主要波長における内部吸光度が0.020以上である請求項1又は請求項2に記載の透過型液晶表示装置。 3. The transmissive liquid crystal display device according to claim 1, wherein the light diffusion layer has an internal absorbance of 0.020 or more at a main wavelength of light emitted from the backlight light source.
  4.  前記光拡散層は、前記バックライト光源から発せられた光の主要波長における内部吸光度が0.028以上0.062以下である請求項1~請求項3のいずれか1項に記載の透過型液晶表示装置。 The transmissive liquid crystal according to any one of claims 1 to 3, wherein the light diffusion layer has an internal absorbance of 0.028 or more and 0.062 or less at a main wavelength of light emitted from the backlight light source. Display device.
  5.  前記光拡散層中の前記散乱子の含有濃度が、前記光拡散層の膜厚方向において前記液晶セル側で高い請求項1~請求項4のいずれか1項に記載の透過型液晶表示装置。 The transmissive liquid crystal display device according to any one of claims 1 to 4, wherein a content concentration of the scatterers in the light diffusion layer is high on the liquid crystal cell side in a film thickness direction of the light diffusion layer.
  6.  前記光拡散層が、前記透光性ポリマー中に前記散乱子が分散された散乱層と、前記透光性ポリマー及び前記着色剤を含有する着色層と、の積層体である請求項1~請求項5のいずれか1項に記載の透過型液晶表示装置。 The light diffusion layer is a laminate of a scattering layer in which the scatterers are dispersed in the light-transmitting polymer and a colored layer containing the light-transmitting polymer and the colorant. Item 6. The transmissive liquid crystal display device according to any one of items 5 to 6.
PCT/JP2010/059216 2009-06-09 2010-05-31 Transmission type liquid crystal display device WO2010143552A1 (en)

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TWI425275B (en) 2014-02-01
JP5323190B2 (en) 2013-10-23

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