WO2009081735A1

WO2009081735A1 - Backlight device and liquid crystal display device

Info

Publication number: WO2009081735A1
Application number: PCT/JP2008/072423
Authority: WO
Inventors: Ken'ichi Harai
Original assignee: Zeon Corporation
Priority date: 2007-12-26
Filing date: 2008-12-10
Publication date: 2009-07-02
Also published as: JP5195765B2; TW200951572A; TWI465807B; JPWO2009081735A1

Abstract

Provided are a liquid crystal display device, which has low manufacturing cost, low power consumption and high luminance, and a backlight device for providing such liquid crystal display device. The backlight device is provided with a light source, which has one or more light emitting regions in a wavelength band of 400nm or more but not more than 600nm and one or more light emitting regions in a wavelength band of 600nm or more but not more than 700nm; and a selective reflection element disposed on the side of the light emitting surface of the light source. The selective reflection band of the selective reflection element includes at least a part of the light emitting region in the wavelength band of 600nm or more but not more than 700nm. The liquid crystal display device provided with such backlight device is also provided.

Description

Backlight device and liquid crystal display device

The present invention relates to a backlight device and a liquid crystal display device, and more particularly to a backlight device and a liquid crystal display device with low power consumption and high luminance.

Since display devices such as liquid crystal display devices are required to have characteristics such as high luminance, low cost, low power consumption, and high color reproducibility, various improvements have been proposed.

In a backlight device that supplies light to a liquid crystal panel, a fluorescent tube enclosing a phosphor is often used as a light source. Conventionally, it has been known to use a cold cathode tube (hereinafter referred to as 3CCFL) having a bright line near a wavelength of 611 nm as a red bright line in addition to blue and green bright lines. For the purpose of spreading, in addition to or instead of the red emission line, cold cathode tubes having emission lines near the wavelength of 658 nm (hereinafter referred to as “long wavelength 3CCFL” and “4CCFL”, respectively) are used. Has been done.

However, in general, the cold-cathode tube has a weak red line brightness, and the long wavelengths 3CCFL and 4CCFL in particular have a problem that the red line brightness is particularly low. Furthermore, in order to achieve white balance, it is necessary to suppress the light intensities of the blue and green wavelength components so as to match the red light intensity. As a result, the overall light utilization efficiency is lowered, resulting in a decrease in luminance. Therefore, there is a problem that the power must be increased in order to increase the luminance.

In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. 2007-52398 describes that an LED is combined as a red light source in addition to a cold cathode tube. However, in such a configuration, the temperature characteristics and deterioration characteristics of the cold cathode fluorescent lamp and the LED are different, so that the time-dependent changes in the respective light emission characteristics are different. Therefore, there arises a problem that the white balance, which was good at the time of manufacture, is destroyed over time. Furthermore, the problem that the structure of an apparatus becomes complicated also arises.

An object of the present invention is to provide a liquid crystal display device having high luminance and good white balance, and a backlight device that provides such a liquid crystal display device.

As a result of intensive studies to solve the above problems, the present inventor has provided a selective reflection element that selectively transmits circularly polarized light in a specific wavelength region corresponding to the above-described red emission line in the backlight device. The present inventors have found that the luminance can be improved without increasing the power consumption, and have completed the present invention.

That is, according to the present invention, the following is provided.
[1] A light source having one or more light emission regions in a wavelength band of 400 nm or more and less than 600 nm and one or more light emission regions in a wavelength band of 600 nm or more and 700 nm or less, and a selective reflection element provided on the light emission surface side of the light source. The selective reflection wavelength band of the selective reflection element includes at least a part of a light emitting region in the wavelength band of 600 nm to 700 nm.
[2] The light source has one or more long-wavelength red bright lines in the wavelength band of 640 nm or more and 700 nm or less as the light-emitting region, and the selective reflection band of the selective reflection element is at least of the long-wavelength red bright line. The backlight device including one peak wavelength.
[3] The light source further has one or more short-wavelength red emission lines in the wavelength band of 600 nm or more and less than 640 nm as the light-emitting region, and the selective reflection band of the selective reflection element is the short-wavelength side red emission line. The backlight device including at least one peak wavelength.
[4] The backlight device, wherein the selective reflection element has substantially no selective reflection band in a wavelength band of 400 nm or more and less than 600 nm.
[5] The backlight device, wherein the light source includes a cold cathode tube or a light emitting diode.
[6] A liquid crystal display device comprising the backlight device and a liquid crystal panel.

The backlight device of the present invention has low power consumption and high luminance, and in particular, the luminance of the red region that is likely to be insufficient with a normal backlight device is high. Therefore, the liquid crystal display device of the present invention including this can be a liquid crystal display device with low power consumption, high luminance, and good white balance.

FIG. 1 is a perspective view showing an outline of an example of a backlight device of the present invention. FIG. 2 is a side view schematically showing the backlight device shown in FIG. FIG. 3 is a graph showing an emission spectrum of a cold cathode tube that can be used as a light source in the backlight device of the present invention. FIG. 4 is a graph showing a half-value width region of main bright lines by enlarging the region of the wavelength of 600 nm to 700 nm in the graph of FIG.

(Backlight device)
The backlight device of the present invention includes a specific light source and a specific selective reflection element. The selective reflection element is provided on the light exit surface side of the light source in the backlight device. The backlight device of the present invention can further optionally include other components such as a reflection plate and a light diffusion plate.

(light source)
In the present invention, the light source may be a cold cathode tube, a hot cathode tube, a light emitting diode, or a combination thereof, and particularly preferably includes a cold cathode tube or a light emitting diode.

When a light emitting diode (LED) is used as a light source, the configuration of each LED includes, for example, (I) a configuration consisting of only white LEDs, (II) a configuration combining RGB primary colors, and (III) an intermediate color for RGB primary colors. The structure etc. which are combined can be mentioned. Further, when a configuration combining the three primary colors of RGB (the configuration of (II) and (III)) is used, (i) at least one red LED, green LED, and blue LED are arranged close to each other, and each color And (ii) a configuration in which red LED, green LED, and blue LED are appropriately arranged and color display is performed using a field sequential method in which each color LED is colored in a time-sharing manner. Can do.

In the present invention, the light source has one or more light emitting regions in a wavelength band of 400 nm or more and less than 600 nm, and one or more light emitting regions in a wavelength band of 600 nm or more and 700 nm or less. Here, the emission region is a wavelength band in which light emission is observed when an emission spectrum is observed. Here, when the light source is a combination of a plurality of types, the light emission region in the spectrum of all the combined light sources can be set as the specific light emission region. For example, when having a plurality of types of light emitting diodes as a light source as described above, one of them is either a light emitting region in a wavelength band of 400 nm or more and less than 600 nm or a light emitting region in a wavelength band of 600 nm or more and 700 nm or less. One of them may have the other light emitting region.

Preferably, the light source has one or more bright lines as a light emitting region in each of a wavelength band of 400 nm to less than 600 nm and a wavelength band of 600 nm to 700 nm. For example, the light source can have one or more emission lines (hereinafter sometimes referred to as “long wavelength red emission lines”) as emission lines in the wavelength band of 600 nm to 700 nm, preferably in the wavelength band of 640 nm to 700 nm. . More preferably, in addition to the long wavelength side red bright line, one or more bright lines (hereinafter sometimes referred to as “short wavelength side red bright line”) may be included in a wavelength band of 600 nm or more and less than 640 nm.

Specifically, the long wavelength side red bright line and the short wavelength side red bright line can be, for example, bright lines having peak wavelengths in the range of about 650 nm to 668 nm and about 606 nm to 618 nm, respectively.

On the other hand, as one or more emission lines in the wavelength band of 400 nm or more and less than 600 nm, the light source can have, for example, a blue emission line with a peak wavelength of about 430 nm or more and 500 nm or less and a green emission line with a peak wavelength of about 540 nm.

Specific examples of the emission spectrum of the light source described above are shown in FIGS. 3 and 4, 3CCFL having a blue emission line having a peak wavelength of about 430 nm to 500 nm, a green emission line having a peak wavelength of about 540 nm, and a red emission line having a peak wavelength of about 611 nm, and a red emission line having a peak wavelength of about 658 nm. The example of the spectrum of 4CCFL which has is shown. In addition to the example shown here, a long wavelength 3CCFL having only a bright line having a peak wavelength of 658 nm as a red bright line can also be given as a preferred example.

In such a cold cathode tube having blue, green and red emission lines, the luminance of the red emission line is lower than that of the other color emission lines, and the power consumption must be increased in order to increase the luminance of the red emission line. In many cases, however, according to the present invention, a backlight device with low power consumption and good color balance can be configured even when such a cold cathode tube is used.

Specific examples of the light source having the specific emission line include red light emission YOX (Y ₂ O ₃ : Eu ³⁺ ), green light emission LAP (LaPO ₄ : Tb ³⁺ , Ce ³⁺ ), blue light emission BAM (Ba ₂ Al A cold cathode tube having a rare earth phosphor such as ₁₆ O ₂₇ : Eu ²⁺ ) can be preferably exemplified.

(Selective reflection element)
In the present invention, the selective reflection of the selective reflection element means a characteristic that the element transmits a specific polarized light and reflects at least a part of the other light, and the selective reflection band is a selective reflection of the specific element. This refers to the wavelength band where this occurs. For the selective reflection band, the reflection spectrum of the selective reflection element is measured with a spectrophotometer (for example, JASCO V-550 manufactured by JASCO Corporation), and the band with a reflectance exceeding 20% can be set as the selective reflection band. .

In the present invention, the selective reflection band of the selective reflection element includes at least a part of the light emitting region in the wavelength band of 600 nm to 700 nm of the light source. More preferably, the selective reflection band includes at least part of the half-width region of the bright line in the wavelength band of 600 nm to 700 nm of the light source, more preferably includes the peak wavelength of the bright line, and even more preferably the entire half-width region. including.

Further, when the light source has a plurality of light emitting regions in a wavelength band of 600 nm to 700 nm, the selective reflection band of the selective reflection element is described above for at least one, preferably all of the plurality of light emitting regions. Have a relationship. More preferably, the selective reflection element has a selective reflection band over the entire wavelength band of 600 nm to 700 nm.

This will be specifically described with reference to the example of the emission spectrum shown in FIG. For example, the 3CCFL shown in FIG. 4 has an emission line having a peak wavelength of about 611 nm as the emission line having the maximum luminance. The selective reflection band of the selective reflection element preferably includes at least a part of a region having a wavelength of about 610 nm or more and 612 nm or less, which is the half width of the emission line, more preferably includes a peak wavelength of about 610 nm, and even more preferably 600 nm or more and 612 nm. Includes all of the following areas: In addition to the bright line having a peak wavelength of about 611 nm, the 4CCFL shown in FIG. 4 has a bright line having a peak wavelength of about 658 nm and a full width at half maximum of 648 nm to 665 nm as a bright line having the second luminance. The selective reflection band of the selective reflection element preferably includes at least part of the half-width region of the bright line for one of these two bright lines, preferably both, more preferably includes the peak wavelength, and even more preferably includes the half-width region. It is preferable that all of these are included.

In the present invention, the selective reflection characteristic in the wavelength band other than the wavelength band of 600 nm to 700 nm of the selective reflection element is not particularly limited. However, the selective reflection element substantially has a selective reflection band in the wavelength band of 400 nm to less than 600 nm. Preferably not. In the present invention, “substantially has no selective reflection band” means that when the reflection spectrum of the selective reflection element is measured with a spectrophotometer, the reflectance in the band is 20% or less. means. Specifically, when a reflection spectrum is measured with a spectrophotometer in a wavelength band of 400 nm or more and less than 600 nm, if there is no wavelength band with a reflectance exceeding 20% within the wavelength band, substantially selective reflection is performed. Has no bandwidth. The selective reflection element having such characteristics can be obtained by appropriately adjusting components such as a liquid crystal compound and a chiral agent in a cholesteric liquid crystal composition described later.

In the present invention, the selective reflection element may be composed of only one element, or a laminated body composed of a combination of a plurality of elements, and the laminated body as a whole has the selective reflection band. May be.

As long as the selective reflection element used in the present invention has the selective reflection band described above, any material may be used and selective reflection based on any principle may be used. And those containing a circularly polarized light separating sheet, or those containing a combination of this circularly polarized light separating sheet and a retardation film.

When the selective reflection element has a circularly polarized light separating sheet and no retardation film, the selective reflection element transmits only specific circularly polarized light in the selective reflection band, and other light (other circularly polarized light, linearly polarized light, etc.). ) Is reflected. On the other hand, when the selective reflection element is a laminate having a circularly polarized light separating sheet and a retardation film, the selective reflecting element is selectively reflected when the circularly polarized light separating sheet is disposed on the light source side and the retardation film is disposed on the exit surface side. In the band, light obtained by converting specific circularly polarized light into linearly polarized light is emitted. The reflected light is reflected inside the backlight device, and is emitted if it becomes a specific circularly polarized light when entering the selective reflection element again. In the backlight device of the present invention, by performing such selective reflection, specific polarized light can be emitted with high luminance in the selective reflection band and supplied to the liquid crystal panel, thereby improving the luminance of the liquid crystal display device. Can be made.

As an example of the circularly polarized light separating sheet, a composition capable of exhibiting a cholesteric liquid crystal phase (cholesteric liquid crystal composition) is applied to a transparent resin substrate to obtain a cholesteric resin layer, and then at least one time of light irradiation and / or A circularly polarized light separating sheet formed by curing by heating treatment can be mentioned.

As the cholesteric liquid crystal composition, a composition containing a rod-like liquid crystal compound that can be cured by itself or with other substances can be used. Specific examples include rod-like liquid crystal compounds having Δn of 0.18 or more and having at least two or more reactive groups in one molecule.
More specifically, examples of the rod-like liquid crystalline compound include compounds represented by the formula (1).
R ³ -C ³ -D ³ -C ⁵ -MC ⁶ -D ⁴ -C ⁴ -R ⁴ Formula (1)
(Wherein R ³ and R ⁴ are reactive groups, each independently (meth) acryl group, (thio) epoxy group, oxetane group, thietanyl group, aziridinyl group, pyrrole group, vinyl group, allyl group, D ³ and D ⁴ are groups selected from the group consisting of fumarate group, cinnamoyl group, oxazoline group, mercapto group, iso (thio) cyanate group, amino group, hydroxyl group, carboxyl group, and alkoxysilyl group. A group selected from the group consisting of a bond, a linear or branched alkyl group having 1 to 20 carbon atoms, and a linear or branched alkylene oxide group having 1 to 20 carbon atoms; C ³ to C ⁶ are a single bond, —O—, —S—, —S—S—, —CO—, —CS—, —OCO—, —CH ₂ —, —OCH ₂ —, —CH═. N—N═CH—, —NHC O -, - OCOO -, - CH 2 COO-, and .M represents a group selected from the group consisting of -CH ₂ OCO- represents a mesogenic group, specifically, having a substituted or unsubstituted group Azomethines, azoxys, phenyls, biphenyls, terphenyls, naphthalenes, anthracenes, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, 2 to 4 skeletons selected from the group of alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, alkenylcyclohexylbenzonitriles are represented by —O—, —S—, —SS—, —CO—, -CS -, - OCO -, - CH 2 -, - OCH 2 -, - CH = N-N = CH -, - NHCO -, - OCOO , -CH ₂ COO-, and is formed are joined by a linking group of -CH ₂ OCO-, and the like.)
Examples of the substituent that the mesogenic group M may have include a halogen atom, an optionally substituted alkyl group having 1 to 10 carbon atoms, a cyano group, a nitro group, —O—R ⁵ , —O—C. (═O) —R ⁵ , —C (═O) —O—R ⁵ , —O—C (═O) —O—R ⁵ , —NR ⁵ —C (═O) —R ⁵ , —C ( ═O) —NR ⁵ R ⁷ or —O—C (═O) —NR ⁵ R ⁷ . Here, R ⁵ and R ⁷ represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and when it is an alkyl group, the alkyl group includes —O—, —S—, —O—C (= O) —, —C (═O) —O—, —O—C (═O) —O—, —NR ⁶ —C (═O) —, —C (═O) —NR ⁶ —, —NR ⁶ — or —C (═O) — may be present (except when two or more of —O— and —S— are present adjacent to each other). Here, R ⁶ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Examples of the substituent in the “optionally substituted alkyl group having 1 to 10 carbon atoms” include a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, an amino group, and an alkoxy having 1 to 6 carbon atoms. Group, alkoxyalkoxy group having 2 to 8 carbon atoms, alkoxyalkoxyalkoxy group having 3 to 15 carbon atoms, alkoxycarbonyl group having 2 to 7 carbon atoms, alkylcarbonyloxy having 2 to 7 carbon atoms Group, an alkoxycarbonyloxy group having 2 to 7 carbon atoms, and the like.
In the present invention, the rod-like liquid crystalline compound preferably has an asymmetric structure. Here, the asymmetric structure is a structure in which R ³ -C ³ -D ³ -C ⁵ -and -C ⁶ -D ⁴ -C ⁴ -R ⁴ are different in the general formula (1) with the mesogenic group M as the center. Say. By using a rod-like liquid crystal compound having an asymmetric structure, alignment uniformity can be further improved.

In the present invention, the rod-like liquid crystalline compound has a Δn value of 0.18 or more, preferably 0.22 or more. When a compound having an Δn value of 0.30 or more is used, the absorption edge on the long wavelength side of the ultraviolet absorption spectrum may extend to the visible range, but desired optical performance even when the absorption edge of the spectrum extends to the visible range. It can be used as long as it does not adversely affect By having such a high Δn value, a circularly polarized light separating sheet having high optical performance (for example, circularly polarized light separating characteristics) can be provided.

In the present invention, the rod-like liquid crystalline compound preferably has at least two or more reactive groups in one molecule. Specific examples of the reactive group include an epoxy group, a thioepoxy group, an oxetane group, a thietanyl group, an aziridinyl group, a pyrrole group, a fumarate group, a cinnamoyl group, an isocyanate group, an isothiocyanate group, an amino group, a hydroxyl group, and a carboxyl group. , Alkoxysilyl groups, oxazoline groups, mercapto groups, vinyl groups, allyl groups, methacryl groups, and acrylic groups. By having these reactive groups, a stable cured product can be obtained when the cholesteric liquid crystal composition is cured.

In the present invention, the cholesteric liquid crystal composition can optionally contain a crosslinking agent in order to improve the film strength and durability after curing. As the cross-linking agent, it reacts simultaneously when the liquid crystal layer coated with the liquid crystal composition is cured, or heat treatment is performed after curing to accelerate the reaction, or the reaction proceeds spontaneously by moisture to increase the cross-linking density of the liquid crystal layer. Those that can be enhanced and that do not deteriorate the alignment uniformity can be appropriately selected and used, and those that are cured by ultraviolet rays, heat, moisture, etc. can be suitably used. Specific examples of the crosslinking agent include, for example, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 2- (2-vinyl Polyfunctional acrylate compounds such as loxyethoxy) ethyl acrylate; epoxy compounds such as glycidyl (meth) acrylate, ethylene glycol diglycidyl ether, glycerin triglycidyl ether, pentaerythritol tetraglycidyl ether; 2,2-bishydroxymethylbutanol-tris [ 3- (1-aziridinyl) propionate], 4,4-bis (ethyleneiminocarbonylamino) diphenylmethane, trimethylolpropane-tri-β-aziridinyl Aziridine compounds such as lupropionate; Isocyanurate type isocyanates derived from hexamethylene diisocyanate, hexamethylene diisocyanate, isocyanurate type isocyanates, biuret type isocyanates, adduct type isocyanates; polyoxazoline compounds having an oxazoline group in the side chain; vinyltrimethoxysilane; N- (2-aminoethyl) 3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3- (meth) acryloxypropyltrimethoxysilane, N- (1 , 3-dimethylbutylidene) -3- (triethoxysilyl) -1-propanamine and the like. Moreover, a well-known catalyst can be used according to the reactivity of this crosslinking agent, and productivity can be improved in addition to an improvement in film strength and durability.
The blending ratio of the crosslinking agent is preferably 0.1 to 15% by weight in the cured film obtained by curing the cholesteric liquid crystal composition. If the blending ratio of the crosslinking agent is less than 0.1% by weight, the effect of improving the crosslinking density cannot be obtained. Conversely, if the blending ratio is more than 15% by weight, the stability of the cholesteric resin layer is lowered.

In the present invention, the cholesteric liquid crystal composition can optionally contain a photoinitiator. As the photoinitiator, known compounds that generate radicals or acids by ultraviolet rays or visible rays can be used. Specifically, benzoin, benzylmethyl ketal, benzophenone, biacetyl, acetophenone, Michler's ketone, benzyl, benzylisobutyl ether, tetramethylthiuram mono (di) sulfide, 2,2-azobisisobutyronitrile, 2,2-azobis -2,4-dimethylvaleronitrile, benzoyl peroxide, di-tert-butyl peroxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- (4 -Isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-diethylthioxanthone, methylbenzoyl formate, 2,2-dieto Cyacetophenone, β-ionone, β-bromostyrene, diazoaminobenzene, α-amylcinnac aldehyde, p-dimethylaminoacetophenone, p-dimethylaminopropiophenone, 2-chlorobenzophenone, pp'-dichlorobenzophenone, pp ' -Bisdiethylaminobenzophenone, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-propyl ether, benzoin n-butyl ether, diphenyl sulfide, bis (2,6-methoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2-methyl-1 [ 4- (Methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, anthracenebenzophenone, α-chloroanthraquinone , Diphenyl disulfide, hexachlorobutadiene, pentachlorobutadiene, octachlorobutene, 1-chloromethylnaphthalene, 1,2-octanedione, 1- [4- (phenylthio) -2- (o-benzoyloxime)] and 1- [9-Ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl] ethanone 1- (o-acetyloxime), (4-methylphenyl) [4- (2-methylpropyl) phenyl] iodonium Hexafluorophosphate, 3-methyl-2-butynyltetramethylsulfonate Arm hexafluoroantimonate, diphenyl - (p-phenylthiophenyl) sulfonium hexafluoroantimonate, and the like. In addition, two or more compounds can be mixed depending on the desired physical properties, and if necessary, a known photosensitizer or a tertiary amine compound as a polymerization accelerator is added to control curability. You can also.
The blending ratio of the photoinitiator is preferably 0.03 to 7% by weight in the cholesteric liquid crystal composition. When the blending amount of the photoinitiator is less than 0.03% by weight, the degree of polymerization is lowered and the film strength may be lowered. On the other hand, if it is more than 7% by weight, the alignment of the liquid crystal is inhibited and the liquid crystal phase may become unstable.

In the present invention, the cholesteric liquid crystal composition can optionally contain a surfactant. As the surfactant, those not inhibiting the orientation can be appropriately selected and used. As the surfactant, specifically, a nonionic surfactant containing siloxane or fluorinated alkyl group in the hydrophobic group portion can be preferably used, and an oligomer having two or more hydrophobic group portions in one molecule. Is particularly preferred. These surfactants include PF-151N, PF-636, PF-6320, PF-656, PF-6520, PF-3320, PF-651, PF-652 from PolyFox, OMNOVA, FTX- from Neos 209F, FTX-208G, FTX-204D, Seimi Chemical's Surflon KH-40, etc. can be used. The blending ratio of the surfactant is preferably 0.05% to 3% by weight in the cured film obtained by curing the cholesteric liquid crystal composition. When the blending ratio of the surfactant is less than 0.05% by weight, the orientation regulating force at the air interface is lowered and an orientation defect may occur, which is not preferable. On the other hand, when it is more than 3% by weight, it is not preferable because an excessive surfactant may enter between liquid crystal molecules and lower the alignment uniformity.

In the present invention, the cholesteric liquid crystal composition may further contain other optional components as necessary. Examples of the other optional components include a chiral agent, a solvent, a polymerization inhibitor for improving pot life, an antioxidant for improving durability, an ultraviolet absorber, and a light stabilizer. These optional components can be added as long as the desired optical performance is not deteriorated.

The method for producing the cholesteric liquid crystal composition is not particularly limited, and can be produced by mixing the above essential components and optional components.

The circularly polarized light separating sheet can be prepared by applying the cholesteric liquid crystal composition to a transparent resin substrate to obtain a liquid crystal layer, and then curing by at least one light irradiation and / or heating treatment.

The transparent resin substrate is not particularly limited, and a substrate having a thickness of 1 mm and a total light transmittance of 80% or more can be used. Specifically, alicyclic olefin polymers, chain olefin polymers such as polyethylene and polypropylene, triacetyl cellulose, polyvinyl alcohol, polyimide, polyarylate, polyester, polycarbonate, polysulfone, polyethersulfone, modified acrylic polymer, epoxy resin, Examples thereof include a single layer or laminated film made of a synthetic resin such as polystyrene or acrylic resin. Among these, an alicyclic olefin polymer or a chain olefin polymer is preferable, and an alicyclic olefin polymer is particularly preferable from the viewpoint of transparency, low hygroscopicity, dimensional stability, lightness, and the like.

The transparent resin base material may have an alignment film as necessary. By having the alignment film, the cholesteric liquid crystal composition applied thereon can be aligned in a desired direction. The alignment film is subjected to a corona discharge treatment, if necessary, on the substrate surface, followed by cellulose, silane coupling agent, polyimide, polyamide, polyvinyl alcohol, epoxy acrylate, silanol oligomer, polyacrylonitrile, phenol resin, poly A solution in which oxazole, cyclized polyisoprene or the like is dissolved in water or a solvent is applied using a known method such as reverse gravure coating, direct gravure coating, die coating, bar coating, and the like, and then dried. It can be formed by subjecting to rubbing treatment. The thickness of the alignment film may be any film thickness that can achieve the desired alignment uniformity of the cholesteric resin layer, and is preferably 0.001 to 5 μm, and more preferably 0.01 to 2 μm.

Application of the liquid crystal composition to the transparent resin substrate can be performed by a known method such as reverse gravure coating, direct gravure coating, die coating, or bar coating. The thickness of the coating layer of the liquid crystal composition can be appropriately adjusted so that a desired cholesteric resin layer dry film thickness described later can be obtained.

Before the coating layer obtained by the coating is cured, an orientation treatment can be performed as necessary. The alignment treatment can be performed, for example, by heating the coating layer at 50 to 150 ° C. for 0.5 to 10 minutes. By performing the alignment treatment, the cholesteric liquid crystal layer can be aligned well.

A circularly polarized light separation sheet having a cured layer of the cholesteric liquid crystal composition (that is, a cured cholesteric resin layer) can be obtained by curing the cholesteric liquid crystal composition after performing an alignment treatment as necessary. The curing step can be performed by a combination of one or more light irradiations and a heating treatment. Specifically, the heating conditions are, for example, a temperature of 40 to 200 ° C., preferably 50 to 200 ° C., more preferably 50 to 140 ° C., and a time of 1 second to 3 minutes, preferably 5 to 120 seconds. it can. The light used for light irradiation in the present invention includes not only visible light but also ultraviolet rays and other electromagnetic waves. Specifically, the light irradiation can be performed, for example, by irradiating light having a wavelength of 200 to 500 nm for 0.01 second to 3 minutes. Further, for example, a weakly irradiated ultraviolet ray of 0.01 to 50 mJ / cm ² and heating may be alternately repeated a plurality of times to obtain a circularly polarized light separating sheet having a wide reflection band. After expanding the reflection band by the above-mentioned weak UV irradiation, etc., a relatively strong UV light of 50 to 10,000 mJ / cm ² is irradiated to completely polymerize the liquid crystalline compound to form a cured cholesteric resin layer. Can do. The expansion of the reflection band and the irradiation with strong ultraviolet rays may be performed in the air, or a part or all of the process may be performed in an atmosphere in which the oxygen concentration is controlled (for example, in a nitrogen atmosphere). .

In the present invention, the step of applying and curing the cholesteric liquid crystal composition on the transparent resin substrate is not limited to one time, and two or more cured cholesteric resin layers can be formed by repeating coating and curing a plurality of times. .

In the circularly polarized light separating sheet, the dry thickness of the cured cholesteric resin layer is preferably 3.0 μm to 10.0 μm, more preferably 3.5 μm to 8 μm. When the dry thickness of the cured cholesteric resin layer is less than 3.0 μm, the reflectivity is lowered. Conversely, when the thickness is greater than 10.0 μm, the cured cholesteric resin layer is colored when observed from an oblique direction. Therefore, it is not preferable respectively. The dry film thickness refers to the total film thickness of each layer when the cured cholesteric resin layer is two or more layers, and the film thickness when the cured liquid crystal layer is one layer.

In the present invention, the selective reflection element can include a retardation film in addition to the circularly polarized light separating sheet. Specifically, a circularly polarized light separating sheet and a retardation film can be laminated to form a selective reflection element. The lamination can be achieved by integrating the circularly polarized light separating sheet and the retardation film via an adhesive or a pressure-sensitive adhesive. Furthermore, for the purpose of improving the durability and rigidity of the selective reflection element, an additional transparent resin base material is integrated on the transparent resin base material and / or the retardation film via an adhesive or a pressure sensitive adhesive. It can also be made.

As the retardation film used in the present invention, (i) a film-like polymer stretched or (ii) a liquid crystal material applied on a transparent resin substrate, oriented and cured is used. Can do. In the case of using the retardation film of (ii), selective reflection is performed by integrating the retardation film obtained by applying a liquid crystalline material on an appropriate base material, aligning, and curing it with a circularly polarized light separating sheet. It can also be used as an element, or on the circularly polarized light separating sheet of the present invention, if necessary, an alignment film is provided and subjected to various alignment treatments, and a liquid crystalline material is applied thereon, aligned, and cured. By making it, the layer of the retardation film integrated with the circularly polarized light separation sheet can be provided, and it can also be set as a selective reflection element.

Preferred examples of the retardation film used in the present invention include the optically anisotropic elements described below.

In the present invention, the optically anisotropic element can have a retardation Re in the front direction (hereinafter sometimes abbreviated as “Re”) of approximately ¼ wavelength of transmitted light. Here, the wavelength range of the transmitted light can be a desired range required for the selective reflection element of the present invention, and specifically, for example, 400 nm to 700 nm. Further, the retardation Re in the front direction is approximately ¼ wavelength of transmitted light, and the Re value is ± 65 nm from the ¼ value of the center value in the center value of the wavelength range of transmitted light, preferably It means ± 30 nm, more preferably ± 10 nm.

The optically anisotropic element desirably has a thickness direction retardation Rth (hereinafter sometimes abbreviated as “Rth”) of less than 0 nm. The value of retardation Rth in the thickness direction can be preferably −30 nm to −1000 nm, more preferably −50 nm to −300 nm, in the central value of the wavelength range of transmitted light. By adopting such an optically anisotropic element having an Re value and Rth, it is possible to reduce color unevenness of emitted light while improving brightness and reducing brightness unevenness.
Here, the retardation Re in the front direction is represented by the formula I: Re = (nx−ny) × d (where nx is a direction perpendicular to the thickness direction (front direction) and gives the maximum refractive index). Ny represents a refractive index in a direction perpendicular to the thickness direction (in-plane direction) and perpendicular to nx, and d represents a film thickness). The direction retardation Rth is expressed by the formula II: Rth = {(nx + ny) / 2−nz} × d (where nx is a direction perpendicular to the thickness direction (in-plane direction) and gives the maximum refractive index) Ny is the refractive index in the direction perpendicular to the thickness direction (in-plane direction) and orthogonal to nx, nz is the refractive index in the thickness direction, and d is the film thickness. ).
In addition, the retardation Re in the front direction and the retardation Rth in the thickness direction are measured using a commercially available phase difference measuring apparatus, and the optically anisotropic elements are spaced 100 mm apart in the longitudinal direction and the width direction (longitudinal or lateral length). If the distance is less than 200 mm, three points are specified at equal intervals in that direction), and measurement is performed in a lattice point shape over the entire surface, and the average value is obtained.

The material constituting the optically anisotropic element is not particularly limited, but a material having a layer made of styrene resin can be preferably used. Here, the styrene resin is a polymer resin having a styrene structure as a part or all of repeating units, and is polystyrene, styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, p-chlorostyrene. , Styrene monomers such as p-nitrostyrene, p-aminostyrene, p-carboxystyrene, p-phenylstyrene, ethylene, propylene, butadiene, isoprene, acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, acrylic acid Examples thereof include copolymers with other monomers such as methyl, methyl methacrylate, ethyl acrylate, ethyl methacrylate, acrylic acid, methacrylic acid, maleic anhydride, and vinyl acetate. Among these, polystyrene or a copolymer of styrene and maleic anhydride can be suitably used.

The molecular weight of the styrenic resin used for the optically anisotropic element is appropriately selected according to the purpose of use, but is the weight average molecular weight (Mw) of polyisoprene measured by gel permeation chromatography using cyclohexane as a solvent. In general, it is 10,000 to 300,000, preferably 15,000 to 250,000, more preferably 20,000 to 200,000.

The optically anisotropic element preferably has a laminated structure of a layer made of the styrene resin and a layer containing another thermoplastic resin. By having the laminated structure, it is possible to provide an element that has both the optical characteristics of the styrene resin and the mechanical strength of other thermoplastic resins. Other thermoplastic resins include alicyclic olefin polymer, methacrylic resin, polycarbonate, acrylate-vinyl aromatic compound copolymer resin, methacrylic ester-vinyl aromatic compound copolymer resin, polyethersulfone, etc. Can be mentioned. Among these, a resin having an alicyclic structure or a methacrylic resin can be preferably used.

The alicyclic olefin polymer is an amorphous olefin polymer having a cycloalkane structure or a cycloalkene structure in the main chain and / or side chain. Specifically, (1) norbornene polymer, (2) monocyclic olefin polymer, (3) cyclic conjugated diene polymer, (4) vinyl alicyclic hydrocarbon polymer, and these A hydride etc. are mentioned. Among these, norbornene-based polymers are more preferable from the viewpoints of transparency and moldability. Examples of these resins having an alicyclic structure include those described in JP-A No. 05-310845, JP-A No. 05-097978, and US Pat. No. 6,511,756.

Specific examples of the norbornene-based polymer include ring-opening polymers of norbornene-based monomers, ring-opening copolymers of norbornene-based monomers and other monomers capable of ring-opening copolymerization, hydrides thereof, and norbornene-based monomers. And addition copolymers with other monomers copolymerizable with norbornene monomers.

The methacrylic resin is a polymer having a methacrylic acid ester as a main component, and includes a methacrylic acid ester homopolymer and a copolymer of a methacrylic acid ester and other monomers. Usually, alkyl methacrylate is used. In the case of a copolymer, acrylic acid esters, aromatic vinyl compounds, vinylcyan compounds, etc. are used as other monomers copolymerized with methacrylic acid esters.

As a preferred specific embodiment of the optically anisotropic element used in the present invention, a multilayer film formed by laminating a film (b layer) made of another thermoplastic resin on both surfaces of a film (a layer) made of polystyrene resin. A stretched multilayer film formed by stretching can be mentioned. Hereinafter, this specific embodiment will be described.

As the polystyrene resin constituting the a layer, the same “styrene resin” as described above can be used.

The polystyrene resin constituting the a layer preferably has a glass transition temperature of 120 ° C. or higher, more preferably 120 to 200 ° C., and further preferably 120 to 140 ° C.

In the present invention, the polystyrene resin and the other thermoplastic resin have Tg (a)> Tg (b) when their glass transition temperatures are Tg (a) (° C.) and Tg (b) (° C.), respectively. ) It is preferable to satisfy the relationship of + 20 ° C. By satisfying such a relationship, optical anisotropy can be effectively given to the a layer made of polystyrene resin when stretched, and a good optical anisotropic element can be obtained.

The method of laminating the polystyrene resin that is the material of the a layer and the other thermoplastic resin that is the material of the b layer to form a multilayer film is not particularly limited, but is a coextrusion T-die method, coextrusion inflation Known methods such as a method of forming by coextrusion such as a method, a coextrusion lamination method, a film lamination forming method such as dry lamination, and a coating forming method may be appropriately used. Among these, a molding method by coextrusion is preferable from the viewpoints of production efficiency and that volatile components such as a solvent do not remain in the film. The extrusion temperature can be appropriately selected according to the type of the polystyrene resin used and the other thermoplastic resin.

The multilayer film is formed by laminating the b layer on both sides of the a layer. An adhesive layer or a pressure-sensitive adhesive layer can be provided between the a layer and the b layer, but the a layer and the b layer are directly laminated (that is, lamination of a three-layer configuration of b layer / a layer / b layer). Body). In the multilayer film, the thickness of the a layer and the b layer laminated on both sides thereof is not particularly limited, but can preferably be 10 to 300 μm and 10 to 400 μm, respectively.

The stretched multilayer film is formed by stretching the multilayer film. The stretched multilayer film may include an A layer provided by stretching the a layer and a B layer provided by stretching the b layer. The stretched multilayer film is a stretched film having a three-layer structure of B layer / A layer / B layer formed by stretching a laminate of b layer / a layer / b layer of the multilayer film. It is preferable.
The stretching can be preferably performed by uniaxial stretching or oblique stretching, and more preferably by uniaxial stretching or oblique stretching by a tenter.

The front direction retardation Re and the thickness direction retardation Rth of the optically anisotropic element can be produced by appropriately adjusting stretching conditions such as stretching temperature and stretch ratio. The stretching temperature is preferably Tg (a) -10 ° C. to Tg (a) + 20 ° C., more preferably Tg (a) −5 ° C. to Tg (a) + 15 ° C. The draw ratio is preferably 1.05 to 30 times, and more preferably 1.1 to 10 times. If the stretching temperature and the stretching ratio are out of the above ranges, the orientation may be insufficient and the refractive index anisotropy and thus the retardation may be insufficiently developed, or the laminate may be broken.

The thickness of the optically anisotropic element is preferably 50 to 1000 μm, more preferably 50 to 600 μm.

(Configuration of other components and equipment)
As long as the backlight device of the present invention has the above-described specific light source and selective reflection element, there is no particular limitation on the configuration thereof, and the configuration includes a direct type backlight, a sidelight type backlight, and the like. be able to.

The configuration of an example of the backlight device of the present invention will be described with reference to FIGS.
In FIG. 1, a backlight device 100 is a direct type backlight device, includes a cold cathode tube 102 as a light source, further reflects the light from the light source 102, and reflects the light from the light source 102 and the reflective plate 103. A light diffusing plate 101 that diffuses light is also included. As a configuration for diffusing light, the light diffusing plate 101 has a prism row 101B composed of a plurality of linear prisms 101A on the light emitting surface 111A side. Further, as shown only in FIG. 2 for illustration, a selective reflection element 250 including a circularly polarized light separating sheet 251 and a retardation film 252 is provided so as to cover the light emitting surface 111A of the light diffusing plate 101.

The position of the selective reflection element in the backlight device of the present invention is not limited to the example given above, and can be any position on the light exit surface side of the light source. For example, it can be provided in contact with the light source side surface of the light diffusion plate 101, or can be provided on a layer such as a diffusion sheet or a prism sheet described below.

The backlight device of the present invention can further include arbitrary components such as a diffusion sheet and a prism sheet. The position where these are provided is not particularly limited, but can usually be provided in any order on the light exit surface of the light diffusion plate.

The backlight device of the present invention can appropriately include other components such as a casing and a power supply device necessary for configuring the device.

(Liquid crystal display device)
The liquid crystal display device of the present invention includes the backlight device of the present invention and a liquid crystal panel.

The liquid crystal panel is not particularly limited, and those used in liquid crystal display devices can be used as appropriate. For example, TN (Twisted Nematic) type liquid crystal panel, STN (Super Twisted Nematic) type liquid crystal panel, HAN (Hybrid Alignment Nematic) type liquid crystal panel, IPS (In Plane Switching) type liquid crystal panel, VA (vertical liquid crystal panel) Examples thereof include MVA (Multiple Vertical Alignment type liquid crystal panel), OCB (Optical Compensated Bend) type liquid crystal panel, and the like.

The liquid crystal display device of the present invention can include a selective reflection element different from that included in the backlight device, if necessary. The selective reflection element is not particularly limited, and a known element can be used.

The liquid crystal display device of the present invention can appropriately include other components necessary for configuring the liquid crystal display device, such as a polarizing plate, in addition to the above-described components.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Production Example 1: Preparation of circularly polarized light separating sheet (1)
(1-1: Preparation of transparent resin base material)
Both surfaces of a transparent film made of an alicyclic olefin polymer (trade name “Zeonor film ZF14-100” manufactured by Optes Co., Ltd.) were subjected to corona discharge treatment. An aqueous solution of 5% polyvinyl alcohol was applied to one side of the film using a # 2 wire bar, and the coating film was dried to form an alignment film having a thickness of 0.1 μm. Next, the alignment film was rubbed to prepare a transparent resin substrate having the alignment film.

(1-2: Formation of cured cholesteric resin layer)
A cholesteric liquid crystal composition for preparing a cured cholesteric resin layer having the following composition was prepared.
Solid content 40% by weight
Liquid crystalline compound (Δn (ne-no) = 0.18 rod-shaped liquid crystal compound 94.93 parts by weight Photopolymerization initiator (trade name IRG907 manufactured by Ciba Specialty Chemicals) 3.1 parts by weight Surfactant (Seimi Chemical Co., Ltd., trade name KH-40) 0.11 parts by weight Chiral agent (BASF, trade name LC756) 5.07 parts by weight Solvent Methyl ethyl ketone 154.82 parts by weight

This cholesteric liquid crystal composition was applied to the surface having the alignment film of the transparent resin substrate having the alignment film prepared in (1-1) above using a # 8 wire bar. The coating film was dried at 100 ° C. for 5 minutes and subjected to orientation aging. The coating film was further irradiated with ultraviolet rays of 1.0 mJ / cm ² (UV-A: 365 nm ± 5 nm), held at 100 ° C. for 1 minute, and then irradiated with ultraviolet rays of 500 mJ / cm ² to cure the coating film, A circularly polarized light separating sheet having a cured cholesteric resin layer having a dry film thickness of 4 μm was prepared. When the reflection spectrum of the obtained circularly polarized light separating sheet was measured using a spectrophotometer (JASCO V-550 manufactured by JASCO Corporation), it was found that the reflectance in the wavelength band of 600 nm to 750 nm was 50%. . Moreover, the reflectance in the wavelength band of 400 nm or more and less than 600 nm was 10% on average, and the wavelength band in which the reflectance exceeded 20% did not exist in the region of 400 nm or more and less than 600 nm.

Production Example 2: Preparation of circularly polarized light separating sheet (2)
A circularly polarized light separating sheet was prepared in the same manner as in Production Example 1 except that 95.1 parts of the following polymerizable liquid crystal compound (1) was used as the liquid crystal compound. Compound (1) can be produced by the method described in JP-A-2008-291218. When the reflection spectrum of the obtained circularly polarized light separating sheet was measured using a spectrophotometer (JASCO V-550 manufactured by JASCO Corporation), it was found that the reflectance in the wavelength band of 600 nm to 750 nm was 50%. . Moreover, the reflectance in the wavelength band of 400 nm or more and less than 600 nm was 10% on average, and the wavelength band in which the reflectance exceeded 20% did not exist in the region of 400 nm or more and less than 600 nm.

Production Example 3: Preparation of Retardation Film A monomer composition composed of 97.8% by weight of methyl methacrylate and 2.2% by weight of methyl acrylate was polymerized by a bulk polymerization method to obtain resin pellets.

Rubber particles were produced according to Example 3 of JP-B-55-27576. This rubber particle has a spherical three-layer structure, the core inner layer is a crosslinked polymer of methyl methacrylate and a small amount of allyl methacrylate, and the inner layer is composed of butyl acrylate and styrene as main components and a small amount of acrylic acid. It is a soft elastic copolymer obtained by crosslinking and copolymerizing allyl, and the outer layer is a hard polymer of methyl methacrylate and a small amount of ethyl acrylate. The average particle size of the inner layer was 0.19 μm, and the particle size including the outer layer was 0.22 μm.

70 parts by weight of the resin pellets and 30 parts by weight of the rubber particles were mixed and melt kneaded with a twin screw extruder to obtain a methacrylic acid ester polymer composition A (glass transition temperature 105 ° C.).

By coextruding the methacrylic ester polymer composition A (b layer) and the styrene maleic anhydride copolymer (glass transition temperature 130 ° C.) (a layer) at a temperature of 280 ° C., a b layer / a layer A multilayer film having an average thickness of 45/70/45 (μm) with a three-layer structure of / b layers was obtained. The laminated film is stretched obliquely at a stretching temperature of 134 ° C. and a stretching ratio of 1.8 times so that the slow axis is in a direction inclined by 45 degrees with respect to the MD direction by a tenter stretching machine. Got.

The retardation in the front direction of the optically anisotropic layer was 140 nm, and the retardation in the thickness direction was −85 nm (each numerical value is a measured value after stretching). Further, one side of the optically anisotropic layer was subjected to corona discharge treatment so that the wetting index was 56 dyne / cm. This optically anisotropic layer was used as a retardation film in the following.

Example 1: Production and evaluation of selective reflection element and liquid crystal display device (1-a: Production of selective reflection element)
The circularly polarized light separating sheet obtained in Production Example 1 and the retardation film obtained in Production Example 3 were bonded together with an adhesive to obtain a selective reflection element.
Here, with respect to the adhesive, first, ethylene-vinyl acetate copolymer emulsion (non-volatile content 40% by weight, vinyl acetate content 40% by weight) 40 parts by weight, petroleum resin emulsion (non-volatile content 40% by weight, resin softening point 85). C.) and 35 parts by weight of a paraffin wax emulsion (non-volatile content: 40% by weight, resin softening point: 64 ° C.), and an adhesive composition having a shear storage modulus of 10 MPa at 23 ° C. was prepared. The agent composition was mixed with fine particles having a diameter of 4 μm (shape: spherical, material: polystyrene, refractive index: 1.59). This adhesive was laminated on the cured liquid crystal layer of the circularly polarized light separating sheet so that the average thickness after drying was 20 μm, and using haze (Hazeguard II (manufactured by Toyo Seiki Co., Ltd.), in accordance with JIS K7136. The surface of this film and the corona-treated surface of the retardation film were bonded to each other at 80 ° C. and a nip pressure of 2 kgf / 50 mm using a laminator to obtain a selective reflection element. Obtained.

(1-b: Production of liquid crystal display device)
A commercially available liquid crystal display device (i) equipped with 4CCFL as a light source is disassembled, and the selective reflection element obtained in the above (1-a) is mounted on the emission surface of the backlight, reassembled, and the liquid crystal display device (ii) ) The liquid crystal display device (ii) includes, as main components, a backlight device (including 4CCFL, a reflection plate, a light diffusion plate, a diffusion sheet, and a selective reflection element mounted thereon), a polarizing plate, a liquid crystal panel, and a polarizing plate In this order.
4CCFL which is a light source of the liquid crystal display devices (i) and (ii) has a peak wavelength of about 611 nm and a wavelength of about 658 nm in addition to a blue emission line with a peak wavelength of about 430 nm to 500 nm and a green emission line with a peak wavelength of about 540 nm. It had a red bright line of books.

(1-c: Evaluation)
After adjusting the voltage of the liquid crystal display device (ii) obtained in (1-b) above so that the light transmittance in each of the blue, green, and red pixels is 100%, the front brightness when displaying the red screen, and The front luminance and chromaticity coordinates (x, y) at the time of displaying a white screen were measured with a viewing angle measuring device (ERGSCOPE manufactured by Autronic Melchers). The results are shown in Table 1.

Comparative Example 1
For the liquid crystal display device (i), the same measurement as in (1-c) of Example 1 was performed. The results are shown in Table 1.

Example 2:
A liquid crystal display device (iv) was manufactured in the same manner as in Example 1 except that a commercially available liquid crystal display device (iii) equipped with a long wavelength 3CCFL was used as a light source instead of the liquid crystal display device (i). The measurement was performed. The results are shown in Table 1.
The liquid crystal display device (iv) is originally incorporated in a backlight device (including a long wavelength 3CCFL, a reflection plate, a light diffusion plate, a diffusion sheet, and a selective reflection element mounted thereon) and a liquid crystal display device as main components. It had a polarizing plate, a liquid crystal panel, and a polarizing plate in this order.
The long wavelength 3CCFL which is the light source of the liquid crystal display devices (iii) and (iv) has a peak wavelength of about 658 nm, a blue emission line having a peak wavelength of about 430 nm to 500 nm, and a peak wavelength of about 658 nm. It had a red bright line of books.

Example 3
A liquid crystal display device was produced in the same manner as in Example 1 except that the circularly polarized light separating sheet obtained in Production Example 2 was used, and the same measurement as in Example 1 was performed. The results are shown in Table 1.

Example 4
A liquid crystal display device was produced in the same manner as in Example 2 except that the circularly polarized light separating sheet obtained in Production Example 2 was used, and the same measurement as in Example 1 was performed. The results are shown in Table 1.

Comparative Example 2
The liquid crystal display device (iii) was measured in the same manner as (1-c) in Example 1. The results are shown in Table 1.

The white balance evaluation method in Table 1 is shown below.
Example 1, Example 3 and Comparative Example 1
Chromaticity coordinates (x, y) measured on a white screen display of a commercially available liquid crystal display device (i) equipped with 4CCFL as a light source, and light in each of blue, green, and red pixels in the liquid crystal display device (i) After adjusting the voltage so that the transmittance of the liquid crystal becomes 100%, the liquid crystal display device (i) is reassembled by mounting the selective reflection element obtained in (1-a) above on the emission surface of the backlight, Difference from chromaticity coordinates (x, y) measured in white screen display (Example 1) or difference from chromaticity coordinates (x, y) measured in white screen display without wearing a selective reflection element ( In Comparative Example 1), the case where it was ± 0.002 or less was judged good, and the case where it exceeded ± 0.002 was judged as bad.
Example 2, Example 4 and Comparative Example 2
The chromaticity coordinates (x, y) of a commercially available liquid crystal display device (iii) equipped with a long wavelength 3CCFL as a light source measured on a white screen display, and each of blue, green, and red pixels in the liquid crystal display device (iii) After adjusting the voltage so that the light transmittance is 100%, the liquid crystal display device (iii) is reassembled by mounting the selective reflection element obtained in (1-a) above on the emission surface of the backlight. Difference from chromaticity coordinates (x, y) measured in white screen display (Example 2), or difference from chromaticity coordinates (x, y) measured in white screen display without wearing a selective reflection element The case where (Comparative Example 2) was ± 0.002 or less was judged good, and the case where it exceeded ± 0.002 was judged as poor.
Note that the chromaticity coordinates (x, y) were measured with a viewing angle measuring device (ERGOSCOPE manufactured by Atlantic Melchers).

From the results shown in Table 1, in the liquid crystal display device of the example having a specific selective reflection element, the red front luminance, the white front luminance, and the white balance during white screen display are good, whereas the liquid crystal display device of the comparative example , The red front luminance, the white front luminance, and the white balance when displaying a white screen were inferior.

Claims

A light source having one or more light emitting regions in a wavelength band of 400 nm or more and less than 600 nm and one or more light emitting regions in a wavelength band of 600 nm or more and 700 nm or less, and a selective reflection element provided on the light exit surface side of the light source,
The backlight device, wherein the selective reflection wavelength band of the selective reflection element includes at least a part of a light emitting region in the wavelength band of 600 nm to 700 nm.
The light source has one or more long-wavelength red bright lines in the wavelength band of 640 nm to 700 nm as the light emitting region, and the selective reflection band of the selective reflection element is at least one peak of the long-wavelength red bright line. The backlight apparatus of Claim 1 containing a wavelength.
The light source further has one or more short wavelength red emission lines in the wavelength band of 600 nm or more and less than 640 nm as the light emitting region, and the selective reflection band of the selective reflection element is at least one of the short wavelength side red emission lines. The backlight device according to claim 2, comprising two peak wavelengths.
The backlight device according to claim 1, wherein the selective reflection element has substantially no selective reflection band in a wavelength band of 400 nm or more and less than 600 nm.
The backlight device according to claim 1, wherein the light source includes a cold cathode tube or a light emitting diode.
A liquid crystal display device comprising the backlight device according to claim 1 and a liquid crystal panel.