TWI465807B - A backlight device and a liquid crystal display device - Google Patents

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 which have low power consumption and high luminance.

In a display device such as a liquid crystal display device, in order to obtain characteristics such as high luminance, low cost, low power consumption, and high color reproducibility, various proposals have been made to improve the above characteristics.

In a backlight device for supplying light in a liquid crystal panel, a fluorescent tube in which a phosphor is enclosed is often used as a light source. Such a fluorescent tube, in addition to the use of the known blue and green bright lines, plus the red bright line of the bright cathode tube near the wavelength of 611 nm (hereinafter referred to as 3CCFL), in the expansion color For the purpose of the reproduction range, a cold cathode lamp (hereinafter referred to as "long wavelength 3CCFL" or "4CCFL") having a red bright line or a bright line near the wavelength of 658 nm is used instead of the red bright line.

However, in general, the brightness of the red bright line of the cold cathode lamp is weak, especially the long wavelength 3CCFL and 4CCFL have the problem that the brightness of the red bright line is particularly weak. Moreover, in order to achieve white balance, it is necessary to suppress the light intensity of the blue and green wavelength components to match the red light intensity. As described above, since the overall light use efficiency is lowered and the brightness is also weakened, in order to increase the brightness, there is a problem that power needs to be increased inevitably.

In order to solve the above-mentioned problems, for example, Japanese Laid-Open Patent Publication No. 2007-52398 discloses that an LED as a red light source is combined in a cold cathode tube. However, under the foregoing structure, since the temperature characteristics and deterioration characteristics of the cold cathode tube and the LED are different, the respective light-emitting characteristics may vary with time. Therefore, a good white balance at the time of manufacture may cause collapse due to the passage of time. In addition, there is also a problem that the structure of the device becomes complicated.

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 to which the liquid crystal display device is applied.

In order to solve the above problems, as a result of intensive research, the inventors have found that in a backlight device, by providing a selective reflection element that can selectively pass circularly polarized light corresponding to a specific wavelength region located in the aforementioned red bright line, it is not necessary to improve The present invention has been completed by consuming electric power to increase the brightness.

That is, according to the present invention, the following structure is provided.

(1) A backlight device 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-emitting surface side of the light source, wherein the selective reflection wavelength band of the selective reflection element includes at least a part of the light-emitting region of the wavelength band of 600 nm or more and 700 nm or less.

(2) In the backlight device, the light source has one or more long-wavelength side red bright lines in a 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 Including the aforementioned long wavelength side red bright line at least one peak wavelength.

(3) In the backlight device, the light source has one or more short-wavelength side red bright lines in a 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 The aforementioned short-wavelength side red bright line includes at least one peak wavelength.

(4) In the backlight device described above, the selective reflection element has substantially no reflection band selected in a wavelength band of 400 nm or more and less than 600 nm.

(5) In the backlight device described above, the light source includes a cold cathode tube or a light emitting diode.

(6) A liquid crystal display device comprising the backlight device described above and a liquid crystal panel.

The backlight device of the present invention has low power consumption and high brightness, and is particularly high in brightness in a red area which is insufficient in a conventional backlight device. Therefore, the liquid crystal display device having the present invention can be a liquid crystal display device having low power consumption, high luminance, and good white balance.

(backlight device)

The backlight device of the present invention has a specific light source and a specific selective reflective element. The selective reflection element is provided on the light-emitting surface side of the light source in the backlight device. The backlight device of the present invention may optionally include other structural elements such as a reflecting plate and a light diffusing plate.

(light source)

The light source in the present invention may be a cold cathode tube, a hot cathode tube, a light emitting diode, or a combination of the foregoing structures, and particularly preferably includes a cold cathode tube or a light emitting diode.

In the case of using a light-emitting diode (LED) as a light source, each of the LED structures is composed of, for example, (I) composed of only white LEDs, (II) composed of RGB three primary colors, and (III) intermediate color combinations of RGB three primary colors. Further, when the structure ((II) and (III)) obtained by combining the three primary colors of RGB is used, at least one of the (i) red LED, the green LED, and the blue LED is disposed adjacent to each other, and the white color of the mixed colors is emitted. The structure and (ii) a configuration in which a red LED, a green LED, and a blue LED are appropriately arranged, and each color LED is color-displayed using a field sequential method of color development under time division.

In the present invention, the light source includes 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 light-emitting region refers to a wavelength band which is considered to have light emission in the case where the light-emitting spectrum is observed. Here, when the light source may be a combination of a plurality of types of light sources, the specific light-emitting region may be used as a light-emitting region in the combined full light source spectrum. For example, in the case where a plurality of types of light-emitting diodes are used as the light source, one of them may have a light-emitting region having a wavelength band of 400 nm or more and less than 600 nm and a wavelength of 600 nm or more and 700 nm or less. One of the light-emitting regions of the domain has one of the light-emitting regions, and the other has another light-emitting region.

Preferably, the light source has more than one bright line in each of the light-emitting regions of 400 nm or more and less than 600 nm and in the respective wavelength bands of 600 nm or less and 700 nm or less. For example, the light source has a bright line having a wavelength band of 600 nm or more and 700 nm or less, preferably one or more bright lines of a wavelength band of 640 nm or more and 700 nm or less (hereinafter referred to as "long wavelength side red light" line"). More preferably, one or more bright lines (hereinafter referred to as "short-wavelength side red bright lines") having a wavelength band of 600 nm or more and less than 640 nm are provided in addition to the long-wavelength red bright line.

The long-wavelength side red bright line and the short-wavelength side red bright line are, for example, bright lines having a peak wavelength of about 650 nm or more, 668 nm or less, and about 606 nm or more and 618 nm or less.

On the other hand, as one or more bright lines having a wavelength band of 400 nm or more and less than 600 nm, the light source may have, for example, a blue bright line having a peak wavelength of about 430 nm or more and a range of 500 nm or less and a peak wavelength of about 540. The green light of the nano.

Specific examples of the above-described light source luminescence spectrum are shown in Figs. 3 and 4. 3 and 4 are preferably blue bright lines having a peak wavelength of about 430 nm or more and 500 nm or less, green light lines having a peak wavelength of about 540 nm, and a peak wavelength of about 611 nm red bright lines. The 3CCFL, as well as the 4CCFL spectrum further having a red peak with a peak wavelength of approximately 658 nm. In addition to the above examples, a preferred example is shown as a long wavelength 3CCFL having only a peak wavelength of 658 nm as a red bright line.

In the above-mentioned cold cathode tube having blue, green and red bright lines, the brightness of the red bright line is lower than that of the other bright lines, and in order to increase the brightness of the red bright line, the power consumption must be greatly increased. According to the present invention, when the cold cathode tube is used, a backlight device having a good color balance with low power consumption can be constructed.

The foregoing light source having a specific bright line, a specific example is a red light emitting YOX (Y ₂ O ₃ :Eu ³⁺ ), a green light emitting LAP (LaPO ₄ :Tb ³⁺ , Ce ³⁺ ), and a blue light emitting BAM (Ba ₂ Al ₁₆ O ₂₇ :Eu ²⁺ ) is a cold cathode tube of a rare earth phosphor.

(select reflective element)

In the present invention, the selective reflection of the reflective element is selected such that the element has a characteristic that transmits a specific polarized light and reflects at least a portion of the light other than the specific polarized light. Selecting the reflective band in the specific element means that the element can cause such a Select the wavelength band of the reflection. The reflection band can be selected by using a spectrophotometer (for example, JASCO V-550 manufactured by JASCO Corporation) to measure the reflection spectrum of the selective reflection element, and the band having a reflectance exceeding 20% is referred to as a selective reflection band.

In the present invention, the selective reflection band of the selective reflection element includes at least a portion of the light-emitting region in the wavelength band of the light source of 600 nm or more and 700 nm or less. Preferably, the selection of the reflection band includes at least a portion of the half-value width region of the bright line in the wavelength band of 600 nm or more and 700 nm or less, and more preferably includes a peak wavelength of the bright line, and preferably includes a half-value width region. All.

Further, when the light source has a plurality of light-emitting regions in a wavelength band of 600 nm or more and 700 nm or less, the selective reflection band of the selective reflection element is at least one of the plurality of light-emitting regions, preferably all of The above relationship. More preferably, the reflective element is selected to have a selective reflection band in the wavelength band of 600 nm or more and 700 nm or less.

Please refer to the example of the luminescence spectrum shown in Fig. 4 for specific explanation. For example, in the case of 3CCFL as shown in Fig. 4, it has a peak wavelength of about 611 nm as a bright line having the maximum luminance. The selective reflection band of the selective reflection element preferably comprises at least a portion of the bright line half value wide wavelength of about 610 nm or more and 612 nm or less, more preferably a peak wavelength of about 610 nm, and preferably 600 nm. All of the areas above the meter and below 612 nm. Further, in the case of the 4CCFL shown in Fig. 4, in addition to the peak wavelength of about 611 nm, there is a half-value wide region of 648 nm or more as the second luminance bright line and a peak wavelength of about 658 nm. And the bright line below 665 nm. The selective reflection band of the selective reflective element may comprise one of the aforementioned two bright lines, preferably both, preferably comprising at least a portion of the bright line half value wide region, more preferably comprising a peak wavelength, preferably comprising a half value. All of the wide area.

In the present invention, the selective reflection characteristic of the wavelength band outside the wavelength band of the selective reflection element of 600 nm or more and 700 nm or less is not particularly limited, and may be in a wavelength band of 400 nm or more and less than 600 nm. Does not have a substantial selective reflection band. In the present invention, "there is no substantial selective reflection band" means that the reflection spectrum of the selective reflection element is measured by a spectrophotometer, and the reflectance in the band is 20% or less. Specifically, in the wavelength band of 400 nm or more and less than 600 nm, when the reflection spectrum is measured by a spectrophotometer, when the reflectance in the band does not exceed 20%, it is not essential. The choice of reflection bands. The selective reflection element having the above-described characteristics can be obtained by appropriately adjusting a component such as a liquid crystal compound or a palm powder in a cholesteric liquid crystal composition to be described later.

In the present invention, the selective reflection element may be composed of only one element, or a laminate in which a plurality of elements are combined, wherein the entire laminated body has the selective reflection band.

The selective reflection element used in the present invention does not limit the structure of which material is used as long as it has the selective reflection band, and does not limit the selective reflection by which principle. An example of a preferred selective reflection element is a structure including a circularly polarized light separating sheet, or a combination of the aforementioned circularly polarized light separating sheet and a retardation film.

In the case where the selective reflection element has a circularly polarized light separating sheet, but does not have a phase difference film, the selective reflection element transmits only the circularly polarized light and reflects other light in the selective reflection band (other circularly polarized light, linearly polarized light, etc.) ). On the other hand, the selective reflection element is a laminate having a circularly polarized light separating sheet and a retardation film. When such a selective reflection element is disposed on the light source side of the circularly polarized light separating sheet and the exit surface side of the retardation film, light of a specific circularly polarized light emitted from the reflection band is converted into linearly polarized light. The reflected light is reflected into the backlight device, and when incident on the selective reflection element, a specific circularly polarized light is emitted. In the backlight device of the present invention, by performing the selective reflection, a high-brightness specific polarized light is emitted in the selective reflection band and supplied to the liquid crystal panel, with the result that the brightness of the liquid crystal display device can be improved.

In the example of the circularly polarized light separating sheet, for example, a cholesterol resin layer obtained by coating a cholesteric liquid crystal phase composition (that is, a cholesteric liquid crystal composition) on a transparent resin substrate can be applied. Next, it is obtained by hardening a circularly polarized light separation sheet by light irradiation and/or warming treatment at least once.

The cholesteric liquid crystal composition may be a rod-like liquid crystal compound, and may be a composition obtained by using the rod-like liquid crystal compound itself or curing together with other substances. Specific examples are 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, the rod-like liquid crystalline compound may be a compound 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, and are independently a (meth)acrylic group, a (thio) epoxy group, an oxetanyl group, a propylthio group, an aziridine group, Pyrrolyl, vinyl, allyl, fumarate, cinnamyl, oxazolyl, sulfhydryl, iso(thio)cyanate, amine, hydroxy, carboxyl, and alkoxy Selecting a group consisting of a germyl group. D ³ and D ⁴ are a single bond, a linear or branched chain alkyl group having 1 to 20 carbon atoms, and a linear or branched carbon number of 1 to 20 or The group consisting of bifurcated chain olefin peroxides is selected. C ³ - C ⁶ are single bond combinations, which means from -O-, -S-, -SS-, -CO-, -CS-, -OCO- a group selected from the group consisting of -CH ₂ -, -OCH ₂ -, -CH=NN=CH-, -NHCO-, -OCOO-, -CH ₂ COO-, and -CH ₂ OCO-. M is a representation The mesophase primordium, a specific example may be a non-substituted or substituted group from a carbamide, an azo group, a phenyl group, a diphenyl group, a terphenyl, a naphthalene, an onion, a benzene (a) Acid esters, phenyl cyclohexane carboxylates, cyanobenzene cyclohexanes, cyanide substituted phenyl 2 to 4 skeletons are selected from the group consisting of pyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanthenes, diphenyl(acetyl)acetylenes, and aliphatic alkenylcyclohexylbenzonitriles. Taking -O-, -S-, -SS-, -CO-, -CS-, -OCO-, -CH ₂ -, -OCH ₂ -, -CH=NN=CH-, -NHCO-, -OCOO- , -CH ₂ COO-, and -CH ₂ OCO- and other bonding groups are bonded to form.)

The substituent group of the mesophase primordium M is, for example, a halogen atom, an alkyl group having 1 to 10 carbon atoms having a substituent group, a cyano group, a nitro group, -OR ⁵ , -OC(=O)-R ⁵ , -C (=O)-OR ⁵ , -OC(=O)-OR ⁵ , -NR ⁵ -C(=O)-R ⁵ , -C(=O)-NR ⁵ R ⁷ , or -OC(=O) -NR ⁵ R ⁷ . Here, R ⁵ and R ^{7 each} represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. When an alkyl group is present, the alkyl group may also be via -O-, -S-, or -OC(=O). )-, -C(=O)-O-, -OC(=O)-O-, -NR ⁶ -C(=O)-, -C(=O)-NR ⁶ -, -NR ⁶ -, Or -C(=O)- is formed (however, the case where -O- and -S- are adjacent to each other by two or more are excluded). Here, R ⁶ represents a hydrogen atom or a C 1-6 alkyl group. The substituent in the above "the substituent group may have a carbon number of 1 to 10 alkyl groups" is, for example, a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, an amine group, an alkoxy group having 1 to 6 carbon atoms, or a carbon number. 2 to 8 alkoxyalkoxy groups, alkoxyalkoxy alkoxy groups having 3 to 15 carbon atoms, 2 to 7 alkoxycarbonyl groups having 2 to 7 carbon atoms, or 2 to 7 carbon atoms An alkylcarbonyloxy group, a C 2 to 7 alkoxycarbonyloxy group, or the like.

In the present invention, the rod-like liquid crystalline compound is preferably an asymmetrical structure. Here, the asymmetric structure means that R ³ -C ³ -D ³ -C ⁵ - which is centered on the mesophase primordium M in the general formula (1) is different from -C ⁶ -D ⁴ -C ⁴ -R ⁴ Structure. Since the rod-like liquid crystalline compound has an asymmetric structure, alignment uniformity can be improved.

In the present invention, the Δn value of the rod-like liquid crystal compound is preferably 0.18 or more, more preferably 0.22 or more. When a compound having a Δn value of 0.30 or more is used, the absorption end on the long wavelength side of the ultraviolet absorption spectrum sometimes may be in the visible region, but as long as the aforementioned spectral absorption end is in the visible region, the optical properties are not determined. It can have an adverse effect and can be used. By means of this 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 crystal compound preferably has at least two or more reactive groups in one molecule. Specific examples of the aforementioned reactive group are an epoxy group, a thioepoxy group, an oxetanyl group, a propylsulfonyl group, an aziridine group, a pyrrolyl group, a fumarate group, a cinnamyl group, an isocyanate group. , isothiocyanate group, amine group, hydroxyl group, carboxyl group, alkoxymethyl group, oxazolidine group, fluorenyl group, vinyl group, allyl group, methacryl group and propylene group. By having the aforementioned reactive group, a stable cured product can be obtained when the cholesteric liquid crystal composition is hardened.

In the present invention, the cholesteric liquid crystal composition may include any bridging agent in order to improve film strength and durability after curing. The bridging agent may be simultaneously reacted with the liquid crystal layer coated with the liquid crystal composition, or may be subjected to heat treatment to promote the reaction after hardening, or may be naturally reacted by moisture to increase the density of the liquid crystal layer bridging, and Materials which deteriorate the alignment uniformity are optional, and it is preferred to use ultraviolet rays, heat, moisture, or the like for hardening. Specific examples of bridging agents are trimethylolpropane tri() acrylate, pentaerythritol tri() acrylate, pentaerythritol tetra() acrylate, dipentaerythritol hexa(meth) acrylate, 2-(2-vinyloxy). Polyfunctional acrylate compound such as ethoxy)ethyl acrylate; epoxy propyl (meth) acrylate, ethylene glycol diepoxypropyl ether, glycerol triepoxypropyl ether, pentaerythritol tetraepoxypropyl ether, etc. Epoxy compound; 2,2-bishydroxymethylbutanol-tris[3-(1-ethylimino)propionic acid], 4,4-bis(ethyleneiminocarbonylamino)diphenylmethane, three Aziridine compound such as methylolpropane tris-β-ethyliminopropionic acid; hexamethylene diisocyanate, isocyanurate type isocyanate derived from hexamethylene diisocyanate, diuretic isocyanate, addition isocyanate, etc. Isocyanate compound; polyoxazolium compound with oxazolidine group in the side chain; ethylene trimethoxy decane, N-(2-aminoethyl)-3-aminopropyltrimethoxy decane, 3-aminopropyltrimethoxy Baseline, 3-glycidoxypropylpropyltrimethoxydecane, 3-(m-)propenyloxypropylpropyltrimethoxydecane, N-(1,3- Methylbutylidene) -3- (triethoxysilyl silicon alkyl) -1-propane amine, alkyl alkoxy silicon compound. Further, a known catalyst corresponding to the reactivity of the above-mentioned bridging agent can be used, and in addition to improving the film strength or durability, productivity can be further improved.

The bridging agent blending ratio is preferably a hardening film obtained by hardening a cholesteric liquid crystal composition, and preferably 0.1 to 15% by weight of a bridging agent is used. When the proportion of the bridging agent is less than 0.1% by weight, the effect of increasing the bridging density is not obtained. Conversely, when the ratio of the bridging agent is more than 15% by weight, the stability of the cholesterol resin layer may be lowered.

In the present invention, the cholesteric liquid crystal composition may optionally contain a photoinitiator. As the photoinitiator, a known compound which generates a radical or an acid by ultraviolet rays or visible light can be used. Specifically, for example, benzoin, benzyl methyl ketal, benzophenone, butanedione, acetophenone, mischrone, benzyl, benzyl isobutyl ether, one (two Sulfurized tetramethylthiuram, 2,2-azobisisobutyronitrile, 2,2-azobis-2,4-dimethylvaleronitrile, benzamidine 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, sultone, 2-chlorosultone, 2-methyl ketoxime, 2,4-diethyl ketoxime, methotrexate, 2,2- Diethoxyethyl benzene, β-ionone, β-bromostyrene, diazoaminobenzene, α-pentyl cinnamaldehyde, p-dimethylamine acetophenone, p-dimethylamine benzene Acetone, 2-chlorobenzophenone, pp'-chlorobenzophenone, pp'-bisdiethylamine benzophenone, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-propyl ether, benzoin n-Butyl ether, diphenyl sulfide, bis(2,6-methoxybenzoinyl)-2,4,4-trimethylpentylphosphine oxide, 2,4,6-trimethylbenzoinyl Phenylphosphine oxide, bis(2,4,6-trimethyl) Phenyl phenyl) phenylphosphine oxide, 2-methyl-1-(4-(methylthio)phenyl)-2-hydrazinopropan-1-one, 2-benzyl-2-pyrene Amino-1-(4-ythylphenyl)-butyl-1-one, onion benzophenone, α-chloropurine, diphenyldisulfide, hexachlorobutadiene, pentachloro (generation) butadiene, octachlorobutene, 1-chloromethylnaphthalene, 1,2-octanedione, 1-[4-(phenylthio)-2-(o-benzidine)] or 1-[9-ethyl-6-(2-methylbenzhydrazin)-9H-indazol-3-yl]ethyl ether-1-(o-ethylidene), (4-methylphenyl) [4-(2-methylpropyl)phenyl]iodonium hexafluorophosphate, 3-methyl-2-butynyl ester tetramethylphosphonium hexafluoroantimonate, diphenyl-(p-phenylsulfuric acid) Phenyl phenyl) hexafluoroantimonate. Further, two or more kinds of compounds may be used in combination depending on the desired physical properties, and a third-order amine compound which is a known photo-sensitizer or a polymerization accelerator may be added in accordance with the necessity to control the curability.

The proportion of the above photoinitiator is preferably from 0.03 to 7% by weight in the cholesteric liquid crystal composition. When the amount of the photoinitiator is less than 0.03% by weight, the degree of polymerization is lowered and the film strength is lowered. Conversely, when it is more than 7% by weight, the alignment of the liquid crystal may be impaired and the liquid crystal phase may be unstable.

In the present invention, the cholesteric liquid crystal composition may contain any surfactant. The aforementioned surfactant needs to be appropriately selected to use a structure which does not hinder the alignment. Specifically, the surfactant is preferably a nonionic surfactant containing a decane or a fluorinated alkyl group, and particularly preferably a low polymer having two or more hydrophobic groups in one molecule. The surfactant can be used by OMNOVA PolyFox PF-151N, PF-636, PF-6320, PF-656, PF-6520, PF-3320, PF-651, PF-652, Neos FterGent FTX-209F, FTX-208G, FTX-204D, KH-40 from Surflon Chemical Co., Ltd. Surflon. The surfactant blending ratio is preferably from 0.05% by weight 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 alignment regulating force with the air interface is reduced and the alignment defect is not preferable. Conversely, when the amount is more than 3% by weight, the excess surfactant invades the liquid crystal molecules, resulting in a decrease in alignment uniformity.

In the present invention, the cholesteric liquid crystal composition may further include other optional components as required. Other optional components are, for example, a palmizer, a solvent, a polymerization inhibiting agent for improving pot-life, an antioxidant for improving durability, an ultraviolet absorber, a light stabilizer, and the like. This optional component can be added without degrading the intended optical properties.

The method for producing the cholesteric liquid crystal composition is not particularly limited, and the above-described essential components and optional components may be mixed and produced.

In the circularly polarized light separating sheet, the cholesteric liquid crystal composition is applied onto a transparent resin substrate to obtain a liquid crystal layer, which is then cured by at least one light irradiation and/or a heat treatment.

The transparent resin substrate is not particularly limited, and a substrate having a total light transmittance of 80% or more at a thickness of 1 mm can be used. Specifically, from an alicyclic olefin polymer, a chain olefin polymer such as polyethylene or polypropylene, triethylene fluorene fiber, polyvinyl alcohol, polyimine, polyarylate, polyester, polycarbonate, polyfluorene A single layer or a laminated film composed of a synthetic resin such as a polyether oxime, a denatured propylene polymer, an epoxy resin, a polystyrene or an acrylic resin. Among the above, the alicyclic olefin polymer or the chain olefin polymer is preferred, and the alicyclic olefin polymer is particularly preferable from the viewpoints of transparency, low hygroscopicity, dimensional stability, and lightness.

The transparent resin substrate may be required as needed, and may have an alignment film. By having an alignment film and applying a cholesteric liquid crystal composition on the alignment film, alignment can be performed in a predetermined direction. The alignment film is formed on the surface of the substrate, and after applying corona discharge treatment or the like as needed, the fiber, the decane coupling agent, the polyimine, the polyamine, the polyvinyl alcohol, the epoxy acrylate, and the decyl alcohol are oligomerized. After the solution, polyacrylonitrile, phenol resin, polyoxazole, cyclized polyisoprene or the like is dissolved in water or a solvent to form a solution, etc., using reverse gravure coating, direct gravure coating, die coating, and rod type It is formed by applying and drying by a known method such as coating, and then applying a polishing treatment to the dried coating film. The thickness of the alignment film is a film thickness at which the uniformity of the alignment of the predetermined cholesterol resin layer can be obtained, and the film thickness is preferably 0.001 to 5 μm, more preferably 0.01 to 2 μm.

The application to the liquid crystal composition of the transparent resin substrate can be carried out 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 depending on the dry film thickness of a predetermined cholesterol resin layer to be described later.

Before the coating layer obtained by the aforementioned coating is hardened, the alignment treatment may be applied correspondingly. The alignment treatment is, for example, heating the coating layer between 50 minutes Celsius and 150 degrees Celsius for between 0.5 minutes and 10 minutes. The cholesteric liquid crystal layer can be well aligned by applying this alignment treatment.

After the corresponding alignment treatment is applied, a circularly polarized light separation sheet having a hardened layer of a cholesteric liquid crystal composition (that is, a hardened cholesterol resin layer) can be obtained by curing the cholesteric liquid crystal composition. The hardening process described above can be carried out by a combination of one or more light irradiations and heat treatment. A specific example of the heating condition is a temperature of 40 degrees Celsius to 200 degrees Celsius, preferably 50 degrees Celsius to 200 degrees Celsius, more preferably 50 degrees Celsius to 140 degrees Celsius; time is preferably 1 second to 3 minutes, more preferably It is 5 seconds to 120 seconds. In the present invention, the light used for light irradiation includes not only visible light but also ultraviolet rays and other electromagnetic waves. A specific example of light irradiation is irradiation with light having a wavelength of 200 nm to 500 nm for 0.01 second to 3 minutes. Further, for example, it is possible to alternately perform a slight ultraviolet irradiation and heating of 0.01 mJ/cm 2 to 50 mJ/cm 2 repeatedly to form a circularly polarized light separating sheet having a wide reflection band. After the reflection band expansion by the weak ultraviolet irradiation or the like, the liquid crystal compound is completely polymerized and cured into a cholesterol resin layer by irradiation with relatively strong ultraviolet rays of 50 mJ/cm 2 to 10000 mJ/cm 2 . The reflection band expansion and strong ultraviolet irradiation may be performed under air, or one or all of the above-described processes may be performed in an atmosphere gas (for example, under a nitrogen atmosphere) that controls the oxygen concentration.

In the present invention, the coating and hardening of the cholesteric liquid crystal composition on the transparent resin substrate is not limited to one, and the coating and curing may be repeated a plurality of times to form two or more layers of the cured cholesterol resin layer.

In the above circularly polarized light separating sheet, the dried film thickness of the hardened cholesterol resin layer is preferably from 3.0 μm to 10.0 μm, more preferably from 3.5 μm to 8 μm. When the dried film thickness of the hardened cholesterol resin layer is thinner than 3.0 μm, the reflectance is lowered. On the other hand, when it is thicker than 10.0 micrometers, it is not preferable because coloring is observed from the oblique direction to the hardened cholesterol resin layer. Further, when the thickness of the dried film is two or more layers of the cured cholesterol resin layer, the total thickness of each layer is referred to, and when the layer of the cured liquid crystal layer is one layer, the film thickness of the layer is referred to.

In the present invention, the selective reflection element may have a phase difference film in addition to the circularly polarized light separation sheet. Specifically, a circularly polarized light separating sheet and a retardation film are laminated to serve as a selective reflection element. The laminated circularly polarized light separating sheet and the retardation film can be integrated by an adhesive or an adhesive. Further, in order to enhance the durability and rigidity of the selective reflection element, an additional transparent resin substrate is integrated by the adhesive or the adhesive on the transparent resin substrate and/or the retardation film.

The retardation film used in the present invention is a structure obtained by using (i) a film-like polymer extending; or (ii) coating, aligning, and curing a liquid crystal material on a transparent resin substrate. When the retardation film of (ii) is used, the liquid crystal material is applied, aligned, and cured on a suitable substrate, and the retardation film can be integrated with the circularly polarized light separation sheet as a selective reflection element; or the present invention On the polarized light separation sheet, various alignment treatments can be performed for the alignment film to be provided, and the liquid crystal material can be applied, aligned, and cured, and a phase difference film layer integrated with the circularly polarized light separation sheet can be provided. To obtain a selective reflective element.

Preferred embodiments of the retardation film used in the present invention will be described with the following optical anisotropic elements.

In the present invention, the optical anisotropic element can transmit a retardation Re (hereinafter, abbreviated as "Re") in the front direction of the optical anisotropic element by transmitting a substantially 1/4 wavelength of light. Here, the wavelength range of the transmitted light may be a predetermined 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 a substantially 1/4 wavelength of the transmitted light, which means that the Re value is near the center value of the wavelength range of the transmitted light, preferably from the center value of 1/4 value ± 65 nm, and more. The best is ±30 nm, and the best is within ±10 nm.

Further, the retardation Rth (hereinafter, abbreviated as "Rth") of the optical anisotropic element in the thickness direction is preferably less than 0 nm. The retardation Rth value in the thickness direction is a center value in the wavelength range of the transmitted light, preferably from -30 nm to -1000 nm, more preferably from -50 nm to -300 nm. By using an optical anisotropic element having such a Re value and Rth, it is possible to increase the luminance and reduce the luminance unevenness, and it is also possible to reduce the color unevenness of the emitted light.

Here, the retardation Re in the front direction is Formula I: Re = (nx - ny) × d (wherein nx is a direction inflection indicating a maximum inflection rate given in a direction perpendicular to the thickness direction (front direction)) Rate; ny is a refractive index indicating a direction perpendicular to the thickness direction (in-plane direction) and perpendicular to nx; d represents a film thickness; the value represented by the thickness direction; the retardation Rth in the thickness direction is Formula II: Rth = {(nx+ny)/2-nz}×d (wherein nx is a directional yield ratio indicating a maximum inflection rate given in a direction perpendicular to the thickness direction (in-plane direction); ny means perpendicular to the thickness The direction of the direction (in-plane direction) and the inflection rate in the direction perpendicular to nx; nz is the refractive index in the thickness direction; d is the value indicated by the film thickness.

Further, the retardation Re in the front direction and the retardation Rth in the thickness direction are commercially available phase difference measuring devices, and the optical anisotropic element has a space of 100 mm in the longitudinal direction and the width direction (the length in the longitudinal direction or the lateral direction is insufficient) At 200 mm, three points are specified at equal intervals in this direction, and the grid point measurement is performed comprehensively to obtain an average value.

The material constituting the optical anisotropic element is not particularly limited, and a layer composed of a styrene resin can be used. Here, the styrene resin may be a polymer resin having a part or all of a styrene structure, or may be polystyrene or styrene, α-methylstyrene, o-methylstyrene, ortho-pair. Styrene, p-chlorostyrene, p-nitrostyrene, p-aminostyrene, p-carboxystyrene, p-phenylstyrene and other styrenic monoliths with ethylene, propylene, butadiene, isoprene, Acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, methacrylic acid, methyl methacrylate, ethacrylic acid, methyl methacrylate, acrylic acid, methyl acrylate, anhydrous maleic acid, ethylene acetic acid, etc. A monolithic copolymer or the like. Among them, polystyrene or a copolymer of styrene and anhydrous maleic acid is preferably used.

The molecular weight of the styrene resin used in the optical anisotropic element is appropriately selected depending on the purpose of use, and the weight average molecular weight (Mw) of polyisoprene measured by colloidal permeation chromatography using cyclohexane in terms of a solvent. It is usually 10,000 to 300,000, preferably 15,000 to 250,000, more preferably 20,000 to 200,000.

The optical anisotropic element preferably has a laminated structure of a layer composed of the styrene resin and a layer containing another thermoplastic resin. By having the laminated structure described above, it is possible to obtain an element having both the optical properties of the styrene resin and the mechanical strength of the other thermoplastic resin. The other thermoplastic resin is, for example, an alicyclic olefin polymer, a methacryl resin, a polycarbonate, an acrylate-ethylene aromatic compound copolymer resin, a methacrylate-ethylene aromatic compound copolymer resin, a polyether oxime or the like. Among them, a resin having an alicyclic structure or a methacryl resin is preferably used.

The alicyclic olefin polymer is an amorphous olefin polymer having a cycloalkane structure or a cycloolefin structure in a main chain and/or a side chain. Specifically, (1) a norbornene-based polymer; (2) a monocyclic cyclic olefin-based polymer; (3) a cyclic conjugated diene-based polymer; (4) a vinyl alicyclic carbonization; Hydrogen polymer, the aforementioned hydride, and the like. Among them, a norbornene-based polymer is preferred from the viewpoint of transparency and formability. The resin having such an alicyclic structure is described in Japanese Laid-Open Patent Publication No. Hei 05-310845, Japanese Patent Application Laid-Open No. Hei 05-097978, and No. 6511756.

a norbornene-based polymer, specifically, a ring-opening polymer of a norbornene-based monomer, a ring-opening copolymer between a norbornene-based monomer and another monomer capable of ring-opening copolymerization, and the aforementioned An hydride such as an addition polymer of a norbornene-based monomer, an addition copolymer with another monomer copolymerizable with a norbornene-based monomer, or the like.

a methacrylic resin, which is a polymer mainly composed of methacrylate, for example, a single polymer of methacrylate, a methacrylate of a copolymer of methacrylate and other monomer, Alkyl methacrylate is usually used. In the case of a copolymer, other monocomponents in which the methacrylate is copolymerized are, for example, an acrylate, an aromatic vinyl compound, an ethylene cyanide compound or the like.

A preferred embodiment of the optical anisotropic element used in the present invention is a multilayer obtained by laminating a film (layer b) composed of another thermoplastic resin on both surfaces of a film (layer a) composed of a polystyrene resin. An extended multilayer film obtained by stretching a film. This specific embodiment will be described below.

The polystyrene resin constituting the a layer described above has the same structure as the above-mentioned "styrene resin".

The glass transition temperature of the polystyrene resin constituting the layer a is preferably 120 degrees Celsius or more, more preferably 120 degrees Celsius to 200 degrees Celsius, and most preferably 120 degrees Celsius to 140 degrees Celsius.

In the present invention, the glass transition temperatures of the polystyrene resin and the other thermoplastic resin are TG(a) (°C) and TG(b) (°C), respectively, and preferably TG(a)>TG(b). ) +20 ° C relationship. By satisfying this relationship, it is possible to effectively impart optical anisotropy to the layer a composed of a polystyrene resin, and to obtain a good optical anisotropic element.

The method for forming a multilayer film by laminating the above polystyrene resin as the a layer material and the other thermoplastic resin as the b layer material is not particularly limited, and a co-extrusion T-die method or a co-extrusion blow molding method can be suitably used. A known method such as a co-extrusion molding method such as a lamination method, a film lamination molding method such as dry lamination, and a coating molding method are used. Among them, from the viewpoint of the production efficiency and the fact that the volatile components such as the solvent in the film do not remain, the molding method according to the co-extrusion is preferable. The extrusion temperature is appropriately selected depending on the type of the above-mentioned polystyrene resin to be used and the other thermoplastic resin described above.

In the multilayer film, the b layer is laminated on both sides of the a layer. An adhesive layer or an adhesive layer may be provided between the a layer and the b layer, and it is preferable that the a layer and the b layer are directly laminated (that is, a laminate of the b layer/a layer/b layer and 3 layers). Further, in the multilayer film, the a layer and the thickness of the b layer laminated on both surfaces thereof are not particularly limited, and are preferably 10 to 300 μm and 10 to 400 μm, respectively.

The above-mentioned extended multilayer film is obtained by extending the above-mentioned multilayer film. The above-mentioned extended multilayer film comprises a layer B formed according to the extension of the layer a and a layer B formed according to the extension of the layer b. Preferably, the stretched multilayer film is obtained by extending a laminate of a b layer/a layer/b layer and a three layer structure of the multilayer film to obtain a B layer/A layer/B layer three layer structure.

Preferably, the extension is a uniaxial extension or an oblique extension, preferably a uniaxial extension or an oblique extension by a tenter.

The retardation Re in the front direction and the retardation Rth in the thickness direction of the optical anisotropic element can be produced by appropriately adjusting the stretching conditions such as the stretching temperature or the stretching 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 stretching ratio is preferably from 1.05 to 30 times, more preferably from 1.1 to 10 times. When the extension temperature or the stretching ratio is outside the above range, there are the following problems: the alignment may be incomplete, the anisotropy of the inflection rate, or even the extension delay may not be completely exhibited, or the laminate may be broken.

The thickness of the optical anisotropic element is preferably from 50 to 1,000 μm, more preferably from 50 to 600 μm.

(Other components and device structure)

The backlight device of the present invention is not particularly limited as long as it has the specific light source and the selective reflection element, and may have a structure such as a direct type backlight or a side light type backlight.

An example structure of the backlight device of the present invention described above will be described with reference to Figs. 1 and 2 .

In FIG. 1, the backlight device 100 is a direct-type backlight device, including a cold cathode tube 102 as a light source, and even includes a reflection plate 103 for reflecting light from the light source 102, and light for diffusing light from the light source 102 and the reflection plate 103. Light diffusing plate 101. The light diffusing plate 101 is configured to diffuse light, and has a string 101B composed of a plurality of linear turns 101A on the light emitting surface 111A side. Further, the selective reflection element 250 including the circularly polarized light separating sheet 251 and the retardation film 252 is covered by the light emitting surface 111A of the light diffusing plate 101 via the illustration shown in FIG.

In the backlight device of the present invention, the position of the selective reflection element is not limited to the above example, and may be provided at any position on the light-emitting surface side of the light source. For example, it may be provided in contact with the side surface of the light source of the light diffusing plate 101 or on a layer such as a diffusion sheet or a thin plate.

The backlight device of the present invention may further have any constituent elements such as a diffusion sheet or a thin sheet. These installation positions are not particularly limited, and are usually arranged in an arbitrary order on the light exit surface of the light diffusion plate.

Other parts of the backlight device of the present invention may have components such as a casing and a power supply device which are necessary for the device.

(liquid crystal display device)

The liquid crystal display device of the present invention comprises the backlight device of the present invention and a liquid crystal panel.

The liquid crystal panel is not particularly limited, and can be suitably selected for use in a liquid crystal display device. For example, a twisted nematic (TN (Twisted Nematic)) liquid crystal panel, a super twisted nematic (STN) liquid crystal panel, a hybrid array (HAN (Hybrid Alignment Nematic)) liquid crystal panel, and a lateral electric field drive ( IPS (In Plane Switching) type liquid crystal panel, vertical alignment (VA (Vertical Alignment)) type liquid crystal panel, multiple vertical alignment (MVA (Multiple Vertical Alignment)) type liquid crystal panel, optical compensation board (OCB (Optical Compensated Bend)) Liquid crystal panel, etc.

The liquid crystal display device of the present invention may correspond to other selective reflective elements other than the selective reflective elements including the backlight device. The selective reflection element is not particularly limited, and a known structure can also be used.

In addition to the above-described constituent elements, the liquid crystal display device of the present invention can also have other necessary components constituting the liquid crystal display device, such as a polarizing plate, as appropriate.

[Examples]

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

Production Example 1: Modulation of a circularly polarized light separation sheet (1) (1-1: Modulation of transparent resin substrate)

A corona discharge treatment was performed on both surfaces of a transparent film (manufactured by OPTRONICS Co., Ltd., trade name "ZEONOR FILM ZF14-100") composed of an alicyclic olefin polymer. On the one surface of the film, a 5% polyvinyl alcohol aqueous solution was applied using a wire rod of #2, and the coating film was dried to form an alignment film having a film thickness of 0.1 μm. Next, this alignment film was subjected to a rubbing treatment to prepare a transparent resin substrate having an alignment film. (1-2: Formation of hardened cholesterol resin layer)

The cholesteric liquid crystal composition for constituting the hardened cholesterol resin layer was prepared in the following composition.

Solid fraction 40% by weight

Rod liquid crystal compound having liquid crystal compound (Δn(ne-no)=0.18 94.93 weight unit

Photopolymerization initiator (product name IRG907, manufactured by Ciba Specialty Chemicals Co., Ltd.) 3.1 weight unit

Surfactant (made by Qingmei Chemical Co., Ltd., trade name KH-40) 0.11 weight unit

For palm (BASF company, trade name LC756) 5.07 weight unit

Solvent butanone 154.82 weight unit

The cholesteric liquid crystal composition was coated on the surface of the transparent resin substrate having the alignment film prepared by the above (1-1) using the lead bar of #8. The coating film was dried at 5 degrees Celsius for 5 minutes and conditioned. The coating film was further irradiated with ultraviolet light at 1.0 mJ/cm 2 (UV-A: 365 nm ± 5 nm) and kept at 100 ° C for 1 minute, followed by irradiation with UV curing at 500 mJ/cm 2 . A film was prepared to obtain a circularly polarized light separation sheet having a hardened cholesterol resin layer having a dry film thickness of 4 μm. The reflection spectrum of the obtained circularly polarized light separation sheet was measured using a spectrophotometer (JASCO V-550, manufactured by JASCO Corporation), and it was found that the reflectance was 50% in a wavelength band of 600 nm or more and 750 nm or less. Further, in a wavelength band of 400 nm or more and less than 600 nm, a wavelength band having an average reflectance of 10% and a reflectance of more than 20% does not exist in a region of 400 nm or more and less than 600 nm.

Production Example 2: Modulation of a circularly polarized light separating sheet (2)

In the liquid crystal compound of Production Example 1, a circularly polarized light separation sheet was produced in the same manner as in the following 95.1 weight unit of the above-mentioned superposed liquid crystal compound (1). Further, the compound (1) can be produced by the method described in JP-A-2008-291218. The reflection spectrum of the obtained circularly polarized light separation sheet was measured using a spectrophotometer (JASCO V-550, manufactured by JASCO Corporation), and it was found that the reflectance was 50% in a wavelength band of 600 nm or more and 750 nm or less. Further, in a wavelength band of 400 nm or more and less than 600 nm, a wavelength band having an average reflectance of 10% and a reflectance of more than 20% does not exist in a region of 400 nm or more and less than 600 nm.

【化1】

Production Example 3: Modulation of retardation film

A monomer composition composed of 99.8% by weight of methyl methacrylate and 2.2% by weight of methacrylic acid was polymerized by a bulk polymerization method to obtain resin particles.

Rubber particles were produced in accordance with Example 3 of Japanese Patent Publication No. Sho 55-27576. The rubber particles have a spherical three-layer structure, the core inner layer is a bridge polymer of methyl methacrylate and a small amount of allyl methacrylate, and the inner layer is a butyl acrylate and styrene as a main component and a small amount of allyl acrylate. A soft elastic copolymer obtained by bridging copolymerization, and the outer layer is a hard polymer of methyl methacrylate and a small amount of ethacrylic acid. Further, the inner layer had an average particle diameter of 0.19 μm and the outer layer had a particle diameter of 0.22 μm.

70 parts by weight of the above-mentioned resin particles and 30 parts by weight of the above-mentioned rubber particles were mixed and kneaded by a two-axis extruder to obtain a methacrylate polymer composition A (glass transition temperature of 105 ° C).

The above methacrylate polymer composition A (b layer) and styrene-anhydrous maleic acid copolymer (glass transition temperature of 130 degrees Celsius) (layer a) are co-extruded at a temperature of 280 degrees Celsius to obtain A multilayer film of a b-layer/a-layer/b-layer three-layer structure and each layer having an average thickness of 45/70/45 (micrometers). In the tenter type stretching machine, the laminated film was inclined at an angle of 45 degrees with respect to the MD direction, and obliquely extended at an extension temperature of 134 degrees Celsius and a stretching magnification of 1.8 times to obtain an optical anisotropic layer.

The retardation in the front direction of the optical anisotropy layer was 140 nm, and the retardation in the thickness direction was -85 nm (each value is the measured value after the extension). Further, a corona discharge treatment having a wet index of 56 dynes/cm was applied to one side of the optical anisotropic layer. This optical anisotropic layer used the following retardation film.

Embodiment 1: Preparation and evaluation of selective reflective elements and liquid crystal display devices (1-a: Production of selective reflection elements)

The circularly polarized light separation 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, as an adhesive, 40 parts by weight of an ethylene-ethylene acetate copolymer emulsion (40% by weight of a nonvolatile component and 40% by weight of an ethylene acetate), a petroleum resin emulsion (40% by weight of a nonvolatile matter, and softening of the resin) were prepared. 35 degrees Celsius, 35 weight units, and 10 parts by weight of paraffin wax emulsion (40% by weight of nonvolatile matter, 64 points of softening of resin), and the storage elastic modulus is 10 MPa at 23 degrees Celsius. The composition of the composition was used in such a manner that fine particles (shape: spherical shape, material: polystyrene, refractive index: 1.59) having a diameter of 4 μm were mixed. The adhesive was laminated on the hardened liquid crystal layer of the circularly polarized light separation sheet in an average thickness of 20 μm after drying, and HAZE (HAZE card II (manufactured by Toyo Seiki Co., Ltd.) was used, and JIS K7136 was used as a reference. The measurement was carried out to obtain 60%. The corona-treated surface of this surface and the aforementioned retardation film was bonded using a laminator at a pressure of 80 ° C, 2 kg force / 50 mm to obtain a selective reflection element.

(1-b: Production of liquid crystal display device)

A commercially available liquid crystal display device (i) equipped with a 4CCFL as a light source is decomposed, and the selective reflection element obtained in the above (1-a) is mounted on an emission surface of the backlight, and reassembled to obtain a liquid crystal display device (ii). The main constituent elements of the liquid crystal display device (ii) include a backlight device (including a 4CCFL, a reflection plate, a light diffusion plate, a diffusion thin plate, and the selected selective reflection element), a polarizing plate, a liquid crystal panel, and a polarizing plate.

The 4CCFLs as liquid crystal display devices (i) and (ii) light sources include peak wavelengths in addition to blue bright lines having a peak wavelength of about 430 nm to 500 nm and green bright lines having a peak wavelength of about 540 nm. About 611 nm and 2 red highlights of about 658 nm.

(1-C: Evaluation)

The liquid crystal display device (ii) obtained in the above (1-b) is subjected to voltage adjustment so that the light transmittance of each of the blue, green, and red pixels is 100%, and the viewing angle measuring device (ERGOSCOPE, manufactured by Autronic Melchers Co., Ltd.) Measure the front brightness of the red screen display and the front brightness and chromaticity coordinates (x, y) when the white screen is displayed. The results are shown in Table 1.

Comparative example 1

The same measurement as (1-C) of Example 1 was carried out on the liquid crystal display device (i) described above. The results are shown in Table 1.

Example 2:

A liquid crystal display device (iv) was produced and measured in the same manner as in Example 1 except that a commercially available liquid crystal display device (iii) equipped with a long-wavelength 3CCFL as a light source was used instead of the liquid crystal display device (i). The results are shown in Table 1.

The main components of the liquid crystal display device (iv) include a backlight device (including a long-wavelength 3CCFL, a reflection plate, a light diffusion plate, a diffusion thin plate, and the selected selective reflection element), a polarizing plate on which a liquid crystal display device is originally mounted, and a liquid crystal panel. And polarizing plates.

The long-wavelength 3CCFL which is a light source of the liquid crystal display devices (iii) and (iv) includes, in addition to a blue bright line having a peak wavelength of about 430 nm or more and 500 nm or less, and a green bright line having a peak wavelength of about 540 nm. There is a red bright line with a peak wavelength of about 658 nm.

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. The same measurement as in Example 1 was carried out, and 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. The same measurement as in Example 1 was carried out, and the results are shown in Table 1.

Comparative example 2

The same measurement as (1-C) of Example 1 was carried out with respect to the liquid crystal display device (iii) described above. The results are shown in Table 1.

The evaluation method of white balance in Table 1 is as follows.

‧Example 1, Example 3 and Comparative Example 1

A commercially available liquid crystal display device (i) equipped with a 4CCFL as a light source, the chromaticity coordinates (x, y) measured under the white screen display and the liquid crystal display device (i) are adjusted in voltage to make blue and green After the light transmittance of each of the red pixels is 100%, the selective reflection element obtained in the above (1-a) is mounted on the backlight emission surface and reassembled on the liquid crystal display device (i) to be displayed on a white screen. The difference between the measured chromaticity coordinates (x, y) (Example 1), or the chromaticity coordinates (x, y) measured under the white screen display when the selective reflection element is not installed The difference between the two (Comparative Example 1) is better than ±0‧002 or less, and the case of exceeding ±0.002 is bad.

‧Example 2, Example 4 and Comparative Example 2

A commercially available liquid crystal display device (iii) equipped with a long-wavelength 3CCFL as a light source, a chromaticity coordinate (x, y) measured under a white screen display, and a voltage adjustment of the liquid crystal display device (iii) After the light transmittance in each of the blue, green, and red pixels is 100%, the selective reflection element obtained in the above (1-a) is mounted on the backlight emission surface and reassembled on the liquid crystal display device (iii). The white screen displays the difference between the measured chromaticity coordinates (x, y) (Example 2), or the chromaticity coordinates measured by the white screen display when the selective reflection element is not mounted (x, The difference between y) (Comparative Example 2) is good when it is ±0.002 or less, and it is bad when it exceeds ±0.002.

Further, the chromaticity coordinates (x, y) were measured by a viewing angle measuring device (ERGOSCOPE, manufactured by Autronic Melchers Co., Ltd.).

As is clear from the results shown in Table 1, the liquid crystal display device having the specific selective reflection element embodiment has good white balance in red front luminance, white front luminance, and white screen display. In contrast, the liquid crystal display device of the comparative example is in red. The front brightness, the white front brightness, and the white balance when the white screen is displayed are inferior.

100. . . Backlight device

101. . . Light diffuser

101A. . . Linear 稜鏡

101B. . . Column

102. . . Light source (cold cathode tube)

103. . . Reflective plate

111A. . . Light exit surface

250. . . Selective reflective element

251. . . Circularly polarized light separation sheet

252. . . Phase difference film

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 showing the outline of the backlight device shown in Fig. 1.

Figure 3 is a graph showing the luminescence spectrum of a cold cathode tube which can be used as a light source in the backlight device of the present invention.

Fig. 4 is a view showing a region in which the wavelength of the graph of Fig. 3 is 600 nm or more and 700 nm or less, and the half-value width region of the main bright line is displayed.

101. . . Light diffuser

102. . . Light source (cold cathode tube)

103. . . Reflective plate

111A. . . Light exit surface

250. . . Selective reflective element

251. . . Circularly polarized light separation sheet

252. . . Phase difference film

Claims (5)

A backlight device having 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 less and 700 nm or less, and The selective reflection element on the light-emitting surface side of the light source, wherein the selective reflection wavelength band of the selective reflection element includes at least a part of the light-emitting region of the wavelength band of 600 nm or more and 700 nm or less; and the foregoing selection The reflective element has substantially no selective reflection band in the wavelength band of 400 nm or more and less than 600 nm. The backlight device according to claim 1, wherein the light source has one or more long-wavelength side red bright lines in a wavelength band of 640 nm or more and 700 nm or less as the light-emitting region, and the selective reflection element The aforementioned selective reflection band includes at least one peak wavelength of the aforementioned long wavelength side red bright line. The backlight device according to claim 2, wherein the light source has one or more short-wavelength side red bright lines in a wavelength band of 600 nm or more and less than 640 nm as the light-emitting region, and the selective reflection element The aforementioned selective reflection band includes at least one peak wavelength of the aforementioned short-wavelength side red bright line. The backlight device of claim 1, wherein the light source comprises a cold cathode tube or a light emitting diode. A liquid crystal display device having the first item of the patent application scope The backlight device and the liquid crystal panel are described.