CN100399075C

CN100399075C - Polarizing element, polarizing light source and picture display device using them

Info

Publication number: CN100399075C
Application number: CNB2006101084688A
Authority: CN
Inventors: 原和孝; 宫武稔
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2002-04-23
Filing date: 2003-04-17
Publication date: 2008-07-02
Anticipated expiration: 2023-04-17
Also published as: CN1900749A

Abstract

A polarizer capable of efficiently reflecting an obliquely-transmitting light toward a light source without compromise in transmitting polarization characteristics of a vertically-incident light. A C plate having an oblique phase difference with respect to light inclining at at least 30 DEG of at least lambda/8 is disposed between at least two layers of reflection circular polarizer where selective reflection wavelength bands of polarization are overlap each other. A combination of a reflection linear polarizer and a 1/4 wavelength plate may be used instead of the reflection circular polarizer. Alternatively, a combination of two layers of reflection linear polarizer and two layers of 1/4 wavelength plate (Nz>=2) disposed therebetween can give a similar effect. Further, a combination of two layers of reflection linear polarizer and a 1/2 wavelength plate (Nz>=1.5) disposed therebetween may be used. When reflection linear polarizers are used, they must be pasted together with their axis directions set at a specified angle. The polarizer is preferably used in various imasge display units such as liquid crystal display units and organic EL display units.

Description

Polarization member, polarized light source and use its image display device

The application be submitted on April 17th, 2003, application number is 03809350.2, name is called the dividing an application of Chinese patent application of " polarization member, polarized light source and use its image display device ".

Technical field

The present invention relates to a kind of polarization member, the invention particularly relates to a kind of like this polarization member, this polarization member has fabulous efficient in use aspect the diffused light of light source ejaculation, and be applicable to high brightness polarized light source and various image display device, LCD device as highly-visible, organic EL display, PDP and CRT.

Background technology

For the observability that improves image display device etc., use light beam to focus on to increase the technology of brightness usually towards frontal with light emitted.More specifically, for example focus on and the refraction of parallelization light beam and reflection and use lens, mirror (reflection horizon), prism etc., increase brightness thus in order to utilize.

For example, in LCD device, the light beam of light emitted focuses on along frontal by prismatic lens etc., thereby makes light beam enter LCD device effectively to increase brightness.But owing to need big refringence in principle when focusing on by means of prismatic lens, so this prismatic lens must be arranged via air layer etc.This may cause the optical loss that causes because of unnecessary reflection or scattering.Another problem is to need a large amount of parts.

For the another kind of technology that increases emission brightness in the polarization, proposed to use the brightness of retroreflecting (retro-reflection) to increase system.Particularly, this brightness increase system is included on the bottom surface of light guide plate and arranges the reflection horizon, arranges reflective polarizer on light emission surface.The light beam that enters this system is divided into transmitted light and reflected light according to its polarization state, the reflective layer reflects of reflected light on bottom surface of light guide plate, and launch once more to increase brightness from emitting surface.For example, the circular polarization reflection of light by cholesteryl liquid crystal and be separated in for example JP03 (1991)-45906A describes in detail among JP06 (1994)-324333A and JP07 (the 1995)-36032A.But, to compare with the situation that is applied to have strong diffusible light source, a kind of like this brightness increases system with respect to not providing enough effects by the light source that utilizes prismatic lens etc. to improve focussing property in advance.

In order to address the above problem, be used to increase the technology of brightness in research, this technology replaces lens by utilizing the special optical film, mirror, prisms etc. make the parallel beamization from light source.Typical example is a method of utilizing line spectrum source and bandpass filter combination.Example comprises bandpass filter is placed method on line luminous (line-luminescent) light source more specifically, described light source such as CRT or electroluminescence or display device, as the application of Philips or the patent of having authorized, for example, JP 06 (1994)-235900A, JP 02 (1990)-158289A, Tokuhyo 10 (1998)-510671A (the international disclosed open Japanese translation of the PCT of patented claim), US6307604, DE3836955, DE4220289, EP578302, US2002-0034009, WO002/25687, perhaps Japanese Unexamined Patent Application Publication 2001-521643 and Japanese Unexamined Patent Application Publication 2001-16066.Such as among the US2002-0036735 (Fuji photographic film company limited) another example of record technology comprise three wavelength of low-pass filter corresponding to relevant linear light spectral pattern cold cathode ray tube be set.But these technology have following shortcoming, and promptly they can not work to the light source of non-line spectrum, and perhaps they have problems in the selective film that works with respect to specific wavelength in design and manufacturing.In addition, the evaporation inteferometer coating is through being usually used in bandpass filter, but it has following shortcoming, for example in the atmosphere of humidity since the refractive index of film change, so wavelength properties may change.

Utilization is included in the system of describing among the US4984872A (Rockwell international corporation) based on the example of the parallel light system of hologram materials.But this material has higher positive transmissivity, and its reflection-elimination for the oblique incidence light beam is not very high than (reflection-elimination rate).When parallel beam is provided to this system in order to calculated line transmissivity (straight transmittance), because light passes along frontal, therefore be measured as higherly along the transmissivity of frontal, and the oblique incidence light beam is scattered, thereby makes the measured value of transmissivity very low.But this difference can not appear on diffused light source.Therefore, the situation in use system being placed towards the diffusion back-illumination source may not necessarily show its focusing function fully.In addition, there are as permanance problems such as reliability in the material based on hologram aspect its physical property.

Summary of the invention

Therefore, the purpose of this invention is to provide a kind of polarization member, this polarization member can reflect the light of inclination transmission effectively towards light source, and does not reduce vertical incidence optical transmission-polarization (transmission-polarization) character.

In order to address the above problem, polarization member of the present invention comprises two-layer reflective polarizer at least and places retardation layer between this two-layer reflective polarizer, wherein this two-layer reflective polarizer is a reflection circle polarizer layer, one of in clockwise circularly polarized light of its transmission selectively or the counter-clockwise circularly polarized light, simultaneously reflect another selectively, wherein this two-layer reflection circle polarizer has be used for that having of polarized light select reflection a plurality of the reflection wavelength of selection band is arranged, these wavelength bands overlap each other at least in part, and retardation layer satisfies formula (I) and condition (II).

R≤(λ/10) (I)

R’≥(λ/8) (II)

Wherein at formula (I) with (II), λ represents to enter the light wavelength of retardation layer;

R represents with respect to the incident light from Z-direction of principal axis (normal direction), the absolute value of the delay between X-direction of principal axis and Y-axis-direction (postponing in the face), here, the X-direction of principal axis is the direction (slow-axis direction in the face) of largest refractive index in the display delay layer plane, the Y-direction of principal axis is a direction (quick shaft direction in the face) vertical with the X-direction of principal axis in the retardation layer plane, the Z-direction of principal axis is the thickness direction of retardation layer, and vertical with the Y-direction of principal axis with the X-direction of principal axis;

R ' expression is with respect to the incident light from the 30 ° of directions that tilt at least about the Z-direction of principal axis, the absolute value of the delay between X '-direction of principal axis and Y '-direction of principal axis, here, X '-direction of principal axis be with the perpendicular retardation layer plane of the incident direction of incident light in axial direction, this incident light tilts 30 ° at least about the Z-direction, and Y '-direction of principal axis is and incident direction and the perpendicular direction of X '-direction of principal axis.

Description of drawings

Structure shown in Fig. 1 represents that simultaneously focusing and the brightness in specific embodiment of polarization member of the present invention strengthens, here, and with reflection circle polarizer and the combination of C-plate;

Fig. 2 is according to the present invention, and the explanatory of a plurality of symbols of representing natural light, circularly polarized light and linearly polarized light is shown;

Fig. 3 is the circularly polarized synoptic diagram by combination line polarizer and quarter wave plate;

Fig. 4 illustrates the structure that expression focuses on and brightness strengthens simultaneously in specific embodiment of polarization member of the present invention, here, with the reflected ray polarizer, C-plate and quarter wave plate combination;

Fig. 5 is the synoptic diagram that shows by the formed angle of each layer in Fig. 4 polarization member;

Fig. 6 illustrates the structure that expression focuses on and brightness strengthens simultaneously in specific embodiment of polarization member of the present invention, here, and with reflected ray polarizer and quarter wave plate (Nz 〉=2) combination;

Fig. 7 is the synoptic diagram that shows by the formed angle of each layer in Fig. 6 polarization member;

Fig. 8 illustrates the structure that expression focuses on and brightness strengthens simultaneously in specific embodiment of polarization member of the present invention, here, and with reflected ray polarizer and half-wave plate (Nz 〉=1.5) combination;

Fig. 9 is the synoptic diagram that shows by the formed angle of each layer in Fig. 8 polarization member;

Figure 10 is the synoptic diagram that shows an example of the optical property of bearing the C-plate;

Figure 11 comprises the vertically synoptic diagram of the retardation layer of the liquid crystal molecule of (homeotropically) orientation;

Figure 12 is the synoptic diagram that comprises the retardation layer of disc (discotic) liquid crystal;

Figure 13 is the synoptic diagram that comprises the retardation layer of inorganic layered compound;

Figure 14 shows polarization member according to the present invention at combined reflected linear polarizer, the example in conjunction with angle (bonding angle) under the situation of C-plate and quarter wave plate between each layer;

Figure 15 is the explanatory of representing with the Poincare spheroid, and the transduction pathway of light beam in the polarization member of Figure 14 is shown;

Figure 16 illustrates the focusing of polarization member of example 1 and the curve map that brightness increases performance;

Figure 17 illustrates the focusing of polarization member of example 5 and 6 and the curve map that brightness increases performance.

Embodiment

Then, will be described below each specific embodiment of the present invention.

Result as the research of acumen, the inventor has been found that, polarization member of the present invention with said structure has been realized can not reducing vertical incidence optical transmission-polarization properties of front face brightness being done contribution simultaneously to the usable reflection towards the light of light source incline ground transmission.By making inclination transmitted light (polarization by reflection) change into and can make the light beam of contribution, can also further highlight for strengthening front face brightness towards source reflection.In addition, because polarization member of the present invention has the brightness enhancement function because of focusing and retroreflecting, therefore with regard to focusing function and parallel light function, depend on to the less degree of polarization member of the present invention the type of light source.

In retardation layer of the present invention, as mentioned above, postpone R in the face and be no more than (λ/10), from keeping aspect from Z-direction of principal axis (normal direction) polarization of incident light attitude, preferably should reduce as much as possible to postpone in the face, preferred λ/20 or littler, more preferably λ/50 or littler are desirably zero.This do not have or have only the retardation layer that postpones in the minimal face and only have a delay at thickness direction to be called as the C-plate, and optical axis is positioned on the thickness direction perpendicular to the face direction in this plate.When below the optical property condition (optical property condition) of C-plate satisfies during formula (VI), be referred to as positive C-plate, when below the optical property condition of C-plate satisfies during formula (VII), be referred to as and bear the C-plate.The example of typical negative C-plate comprises the film of biaxial stretch-formed polycarbonate (PC) and polyethylene terephthalate (PET), having to have selects the reflection wavelength band to be set to the cholesteric liquid crystal film shorter than visible light, have film with respect to the disc liquid crystal of plane parallel orientation, and can be by being orientated the product that obtains in the face with negative mineral crystal compound that postpones.The example of typical positive C-plate comprises vertical orientated liquid crystal film.

nx≈ny＜nz (VI)

nx≈ny＞nz (VII)

In the present invention, nx, ny and nz be illustrated in as in each optical layers of above-mentioned C-plate along the X-axle, the axial refractive index of Y-axle and Z-.The X-direction of principal axis is the direction (slow-axis direction in the face) that is presented at largest refractive index in this layer plane, the Y-direction of principal axis is a direction (quick shaft direction in the face) vertical with the X-direction of principal axis in this layer plane, the Z-direction of principal axis is the thickness direction of this layer, and vertical with the Y-direction of principal axis with the X-direction of principal axis.

Retardation layer among the present invention is unrestricted, especially as long as it satisfies formula (I) and optical property condition (II).For example, retardation layer is preferably included under the planar orientation state fixing cholesteric liquid crystal compound, and have the wavelength coverage that is different from visible region (380nm to 780nm) in, exist selection reflection wavelength band arranged.Here, this has the wavelength coverage of selecting the reflection wavelength band to be set to be different from visible region (380nm to 780nm), to avoid the colour developing (coloration) etc. in visible region.Having of cholesteric liquid crystal layers selects the reflection wavelength band clearly to determine according to the cholesteric chirality spacing (cholesteric chiral pitch) and the refractive index of liquid crystal, and has the central wavelength lambda of the reflection selected to represent by following formula (VIII).

λ＝np (VIII)

In formula (VIII), n represents the mean refractive index of cholesteric liquid crystal molecules, and p represents the chirality spacing.

There is the value of the centre wavelength of selecting the reflection wavelength band to be positioned at the wavelength coverage longer, for example, can be positioned at the near infrared radiation district than visible wavelength.But this value more preferably is positioned at the ultraviolet region that is no more than 350nm, because under the situation of influences such as optical activity, the there any complex phenomena can not occur basically.

Though this cholesteryl liquid crystal is not particularly limited, and can suitably select, its example comprise by the polymerisable liquid crystal that the liquid crystal monomer polymerization is obtained, high temperature show cholesteryl liquid crystal character liquid crystal polymer, and composition thereof.Though cholesteryl liquid crystal character can be molten cause or thermic, from being easy to control and be easy to form the aspect of single domain (monodomain), preferred thermotropic liquid crystal.Similarly, the method for especially making cholesteryl liquid crystal is unrestricted, but can suitably adopt any known method.Especially it is unrestricted to can be used in the material of producing partial cross-linked polymeric material, and this polymeric material has cholesteryl liquid crystal character.Example comprises as Tokuhyo2002-533742 (WO00/37585) arbitrarily, EP358208 (US5211877), and the material of describing among the EP66137 (US4388453).Cholesteryl liquid crystal also can obtain by for example nematic crystal monomer or polymerizable liquid-crvstalline unit (mesogenic) compound being mixed and react with chiral reagent.This polymerizable liquid-crvstalline unit compound is especially unrestricted, and its example can be at WO93/22397, EP0261712, DE19504224, disclosed compound among DE4408171 and the GB2280445.Can use non-chiral compound or chipal compounds, these compounds can be single, double or many reactions, can be synthetic in a kind of known mode.The object lesson of polymerizable liquid-crvstalline unit compound comprises trade name LC242 (being produced by BASF AG), trade name E7 (being produced by Merck company limited) and trade name LC-Sillicon-CC3767 (being produced by Wacker-Chemie GmbH).Especially also without limits, but can synthesize by the method for for example in WO98/00428, describing for chiral reagent.More specifically, can use non-polymerizable chiral compound, as trade name S101, trade name R811, trade name CB15 (being produced by Merck company limited) perhaps uses chiral reagent, as trade name LC756 (being produced by BASF AG).

The method that is used to make the retardation layer that contains cholesteric liquid crystal compound is not particularly limited, but can suitably use the conventional known method of making cholesteric liquid crystal layers.An one example comprises that the substrate (base) that has alignment films from the teeth outwards is last or apply cholesteric liquid crystal compound in the substrate that has the liquid crystal aligning ability independently, with this compound orientation, and fixes this state of orientation.

For example, this substrate can be by form the film of polyimide, polyvinyl alcohol (PVA), polyester, polyarylate, polyamide-imides, polyetherimide etc. on the substrate with as far as possible little birefringence delay such as Triafol T or amorphous polyolefin, and the oriented layer that obtains with the surface of these films of friction such as rayon, or the oriented layer that obtains by the SiO2 layer that in similar substrate, forms the deflection deposition.Other examples comprise the substrate that has the liquid crystal aligning ability by stretching polyethylene terephthalate (PET) film or PEN (PEN) film, by further having the meticulous substrate of roughness of accurate orientation control force with the surface of abrasive material such as colcothar or friction fabric processing stretched film, the perhaps substrate that obtains by the oriented layer that forms on stretched film as azobenzene compound, this oriented layer produces orientation control force by optical radiation.

The concrete grammar that forms the retardation layer that contains cholesteric liquid crystal compound in substrate is as follows.At first, the solution of liquid crystal polymer is coated on the substrate surface with liquid crystal aligning ability, and carries out drying in order to form liquid crystal layer.Have no particular limits about solvent, its example comprises chlorinated solvent, as methylene chloride, and triclene and tetrachloroethane; Ketones solvent, as acetone, methyl ethyl ketone (MEK) and cyclohexanone; Aromatic solvent is as toluene; Loop chain alkane is as cycloheptane; Amide solvent, as N methyl pyrrolidone (N-methylpyrrolidone), and ether solvent, as tetrahydrofuran.Above-mentioned solvent may be used singly or in combin.In addition, cladding process is also unrestricted, and can be the known method of a kind of routine, as spin coating, and roller coat, flow coat, printing, dip-coating, film flows and expands (film flow-expanding), and bar is coated with (barcoating) or photogravure.In other method applicatory, the heat fusing product of coating liquid crystalline polymer in a similar fashion, show that preferably the heat fusing product in the state of isotropic phase replaces above-mentioned solution, when keeping melt temperature, make its expansion form thinner layer and it is solidified then as required.This method is being favourable aspect the good working environment health when not using solvent.

Then, the state of orientation of cholesteric liquid crystal molecules is fixed in the liquid crystal layer, to obtain required retardation layer.Fixing means is not particularly limited, but can select and the corresponding any suitable method of purpose of the present invention.For example, liquid crystal layer is heated to glass transition point at least and is lower than the temperature of isotropy phase transition point, thereby produce the planar orientation of liquid crystal polymer molecule, then it is cooled to be lower than the temperature of glass transition point, thereby the formation glassy state makes this orientation fix thus.Perhaps, can also the irradiation by energy such as ultraviolet ray or ion beam be fixed by this orientation in the stage that forms state of orientation.In said process, can also utilize liquid crystal monomer to replace liquid crystal polymer or with liquid crystal polymer, by being orientated and polymerization, thereby provide polymerisable liquid crystal as electron beam and ultraviolet ray or thermal-radiating ionising radiation.Simultaneously, can add chiral reagent or orientation auxiliary agent as required.

For example, when substrate had less birefringence, this substrate can combine with the retardation layer that contains cholesteric liquid crystal compound that is used for polarization member.For example, under the situation of the function that the thickness or the birefringence of substrate can suppress polarization member, can peel off retardation layer, perhaps retardation layer be transferred to another substrate in the use from this substrate.

For retardation layer, preferably also contain the retardation layer of the shaft-like liquid-crystal compounds that in vertical orientated state, solidifies.Though this vertical liquid crystal is not particularly limited, and can suitably select, its example comprises by the polymerisable liquid crystal that the liquid crystal monomer polymerization is formed, the liquid crystal polymer of nematic crystal character under the demonstration high temperature, and composition thereof.Can be by in liquid crystal monomer, adding orientation auxiliary agent etc. as required, and by with such as electron beam and ultraviolet ray or carry out polymerization with thermal-radiating ionising radiation and obtain polymerisable liquid crystal.Though the character of liquid crystal can be molten causing or thermic, from being easy to control and be easy to form the aspect of single domain, preferably thermotropic liquid crystal.Although have no particular limits for liquid crystal monomer, its example comprises polymerizable liquid-crvstalline unit compound.Although have no particular limits for polymerizable liquid-crvstalline unit compound, its example is similar to cholesteryl liquid crystal.

Have no particular limits for the method that forms this retardation layer, but can suitably adopt a kind of known method.For example, under the situation of cholesteryl liquid crystal, can utilize formation retardation layers such as alignment films.For example by go up to apply vertical (homeotropic) liquid crystal at preformed vertical alignment layer (for example long chain alkyl silane), represent and to solidify mesomorphic state vertical orientated to obtain.

In addition, the retardation layer that preferably also contains disc liquid-crystal compounds fixing in nematic phase or column phase (columnar phase) alignment state.For example can be by being illustrated in nematic phase in the disc liquid crystal material with negative uniaxiality or column phase (for example, having the phthalocyanine of the molecule of expansion in the plane or the compound of benzophenanthrene), and fix this state to form this retardation layer.Concrete formation method has no particular limits, and can suitably use known method.

In addition, retardation layer preferably comprises the inorganic layered compound with negative uniaxiality, and this inorganic layered compound is in the state of orientation that the optical axis direction that makes retardation layer is fixed as this plane of vertical son (normal direction).The method that forms this retardation layer has no particular limits, and can suitably adopt known method.The negative inorganic layered compound of uniaxiality describes in detail in JP06 (1994)-82777A.

The synoptic diagram of Figure 11-13 illustrates the retardation layer with fixing vertical orientated state respectively, utilizes the retardation layer of discoid liquid crystal and the retardation layer that is made of inorganic layered compound.In the drawings,

reference marker

1101,1201 and 1301 is represented the vertical liquid crystal molecule respectively, the thin slice of discoid liquid crystal molecule and the inorganic layering compound crystal of negative uniaxiality.

In addition, the retardation layer that contains the non-liquid crystal polymer of biaxial orienting also is preferred.The method that forms this retardation layer has no particular limits, but can suitably use known method.Its example comprises to reach the well balanced biaxial stretch-formed method with the anisotropic polymer film of positive refraction of mode, pushes the method for thermoplastic resin, and the method for cutting parallel-oriented crystal.Perhaps, be coated in the substrate certain non-liquid crystal polymer and drying, form film, thereby obtain the C-plate.Though non-liquid crystal polymer has no particular limits, its preferred example comprises: polyester polymer, as polyethylene terephthalate and PEN; Cellulosic polymer is as biacetyl cellulose and Triafol T; Acrylic acid series polymeric compounds is as polymethylmethacrylate; Styrenic polymer is as polystyrene and styrene-acrylonitrile copolymer (AS resin); Polycarbonate polymer is as the multipolymer of bisphenol-A and carbonic acid; Linearity or branched polyolefin, as tygon, polypropylene, and the rare multipolymer of ethene-third; The polyolefin that comprises ring structure is as polynorbornene; The polyvinyl chloride-base polymkeric substance; Acylamide polymer is as nylon and aromatic polyamide; The acid imide polymkeric substance; The sulfone base polymer; The polyether sulfone polymkeric substance; The polyetheretherketone compounds; The polyphenylene sulfide compounds; The vinyl alcohol compound; The vinylidene chloride base polymer; Ethene butyral base polymer; The arylide base polymer; The polyoxymethylene base polymer; And epoxide polymer.These polymkeric substance may be used singly or in combin.In addition,, for example provide ductility and collapsible character, can add proper additive to these polymeric materials for any purpose.

In addition, the example of non-liquid crystal polymer comprises a kind of resin composition, this resin composition comprises side chain and has the thermoplastic resin that one or more imides that replaced or unsubstituted and side chain have one or more phenyl that replaced or unsubstituted and one or more cyano group.This example is to have to comprise isobutylene and the alternating copolymer of N-methyl maleimide (N-methylmaleimide) and the resin composition of styrene acrylonitrile copolymer.In addition, for the polyimide membrane material, for example can suitably use the material of describing among US5880950 and the US5580964 as the retardation layer that constitutes by non-liquid crystal polymer.

Then, because polarization member of the present invention comprises two polarizer layers (reflection circle polarizer), one of in clockwise circularly polarized light of they transmissions selectively or the counter-clockwise circularly polarized light, and reflect another selectively, therefore, it is favourable for example having the polarization separation function for the natural light with wide-angle incident, thereby can design at an easy rate and make.

Though have no particular limits for the reflection circle polarizer, further preferably the planar orientation state of cholesteryl liquid crystal fixed.Though can suitably select and have no particular limits to this cholesteryl liquid crystal, but when under the situation of retardation layer, for example can use the polymerisable liquid crystal that forms by polymerizable liquid crystal monomer, show the liquid crystal polymer of cholesteryl liquid crystal character under the high temperature, and composition thereof.Polymerisable liquid crystal can be by adding chiral reagent as required in liquid crystal monomer, orientation auxiliary agent etc., and by such as obtaining with electron beam and ultraviolet ray or with the ionising radiation of heat.Though the liquid crystal property of cholesteryl liquid crystal can be molten cause or thermic, from being easy to control and be easy to form the aspect of single domain, is preferably thermotropic liquid crystal.

The example of reflection circle polarizer comprises, more specifically, comprise thin plate with one deck cholesteric liquid crystal polymers, by on glass plate etc. to the described stacked thin plate that forms of putting, and the cholesteric liquid crystal polymers film, although the reflection circle polarizer is not limited to this.Similarly, though have no particular limits for the method that forms these cholesteric liquid crystal layers, for example can be by forming these layers with the similar method of the situation of the retardation layer that comprises cholesteric liquid crystal compound.More preferably, cholesteryl liquid crystal is orientated in layer as far as possible equably.

About the reflection circle polarizer, more preferably, from the aspect of performance of polarization member, this has the reflection wavelength of selection band to cover visible region and light emitted wavelength band, and this has selects the reflection wavelength band clearly to determine according to the courage steroid chirality spacing and the refractive index of above-mentioned liquid crystal.Corresponding with these purposes, for example, the cholesteric liquid crystal layers of forming the reflection circle polarizer can form by a plurality of stacked the putting of selecting to differ from one another in the reflection wavelength band will be arranged.Perhaps, cholesteric liquid crystal layers can be made of simple layer, and in this layer, spacing changes along thickness direction.For stacked a plurality of layers, can also prepare several substrates, cholesteric liquid crystal layers is stacked in the above-mentioned substrate in advance, and then these substrates are stacked.But from reducing aspect such as thickness, further preferable methods is included in and forms an alignment films on the cholesteric liquid crystal layers, and another cholesteric liquid crystal layers is thereon stacked.

Polarization member of the present invention preferably also comprises the layer that has the quarter wave plate function along frontal at least, and this is placed on one of two polarizer layers and is positioned at the outside of that reflection circle polarizer of visible side.Because this structure can become linearly polarized light beam with the circularly polarized light beam that passes the reflection circle polarizer, so that effectively utilize light.Particularly preferably be polarization member and comprise that another absorbs the dichroic polarization plates, this absorption dichroic polarization plates places at least outside the extra play that has the quarter wave plate function on the frontal.

Though have no particular limits for absorbing the dichroic polarization plates, but its example comprises: by adsorb the dichroic material as iodine or dichroic dyestuff in hydrophilic polymer membrane, and the absorbing polarization plate that its stretching is formed, and by being treated to the polyenoid alignment films that the dehydration polyvinyl alcohol (PVA) of removing hydrochloric acid or polyvinyl chloride are made, described hydrophilic polymer membrane such as polyvinyl alcohol film, the polyvinyl alcohol film of part typing (formalized) and based on the partly-hydrolysed film of ethylene-vinyl acetate copolymer.Another example of polarization plates is in order to keep purposes such as waterproof, to form by the protective clear layer of being made by for example plastic coating or overlay film layer is provided at least one surface of this film.To be by contain transparent particulate in protective clear layer form so that produce trickle out-of-flatness from the teeth outwards another example.For example, this transparent particulate is that mean particle diameter is the inorganic particles of 0.5 to 5 μ m, as silica, and alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide and antimony oxide.These particulates can be electric conductivity.In addition, also can use organic fine particles such as crosslinked or uncrosslinked polymkeric substance.

(first embodiment)

Will describe with reference to Fig. 1 and 2 below and represent simultaneously in the polarization member of the present invention to focus on and the mechanism of brightness enhancing.But following explanation only relates to one embodiment of the present of invention, and the present invention is not subjected to the restriction of this explanation.

Fig. 1 illustrates the embodiment of polarization member of the present invention.As shown in the drawing, this polarization member is by stacked cholesteryl liquid crystal circuit polarizer 201 successively (can be referred to as hereinafter ' layer 1 '), C-plate 202 (can be referred to as hereinafter ' layer 2 '), form with the critical piece of cholesteryl liquid crystal circuit polarizer 203 (can be referred to as hereinafter ' layer 3 '), light beam enters from layer 1 side.Among the embodiment shown in this figure, the sense of rotation of passing the circularly polarized light beam of two-layer reflection circle polarizer is identical.Because circuit polarizer or retardation layer all do not have any optical axis that exists along direction in the face, therefore can determine the direction of engagement (bondingdirection) of circuit polarizer and retardation layer arbitrarily.For this reason, the scope at the angle of restriction parallel lightization has isotropy and symmetry characteristic.

Fig. 2 is the explanatory that a plurality of symbols of representing natural light, circularly polarized light and linearly polarized light are shown according to the present invention.Circularly polarized light ' a ' and circularly polarized light ' b ' rotate in opposite direction, and linearly polarized light ' c ' and linearly polarized light ' d ' are each other in right angle intersection.

Desirable principle of operation when entering the polarization member of Fig. 1 below with reference to accompanying drawing order explanation light beam.

(1) at first, from backlight module (light source; Not shown) in the light beam sent into, 1 of the natural light that makes vertical incidence by circuit polarizer 201 (layer 1) is partially and be divided into two circularly polarized light beams, i.e. transmitted light beam 3 and folded light beam 2.The sense of rotation of two circularly polarized light beams is opposite each other.

(2) transmitted light beam 3 passes retardation layer 202 (layer 2) becomes transmitted light beam 4.

(3) transmitted light beam 4 passes circuit polarizer 203 (layer 3) becomes transmitted light beam 5.

(4) transmitted light beam 5 is used for liquid crystal indicator placed on it.

(5) then, the light beam of sending into from backlight module, make 6 of the natural lights of oblique incidence inclined to one side, and be divided into two circularly polarized light beams of transmitted light beam 8 and folded light beam 7 by circuit polarizer 201.These two circularly polarized light beams are with opposite direction rotation.

(6) when transmitted light beam 8 passes retardation layer 202, it has the length of delay of 1/2 wavelength, and becomes transmitted light beam 9.

(7) under the influence that postpones, the circular polarization sense of rotation of transmitted light beam 9 becomes oppositely with respect to light beam 8.

(8) transmitted light beam 9 becomes light beam 10 by circuit polarizer 203 reflections.

The sense of rotation of known circularly polarized light is overturn at reflex time usually (for example referring to " polarized light: produce and use " (" Polarized light:Production and Use "), W.A.Schurcliff, Harvard University Press, Cambridge, Mass.1966).But, know that also by way of exception, sense of rotation (for example can not change under situation about being reflected by cholesteric liquid crystal layers, referring to " Ekisho Jiten (liquid crystal dictionary (Dictionary for Liquid Crystal)) ", pulishedby Baihuukan).Because being reflected on the cholesteryl liquid crystal surface among this figure carried out, so the sense of rotation of circularly polarized light beam 9 and 10 does not change.

(9) when folded light beam 10 is passed retardation layer 202, the influence that is postponed, it becomes transmitted light beam 11.

(10) sense of rotation of transmitted light beam 11 is overturn under the influence that postpones.

(11) sense of rotation of light beam 11 becomes consistently with the sense of rotation of light beam 8 once more, and described light beam 11 passes circuit polarizer 201, becomes transmitted light beam 12.

(12) light beam 7 and light beam 12 turn back to backlight module one side and recycle.These light beams that return are reflected repeatedly, become near the light beam that can pass polarization member normal direction up to them, by placing diffusing panel above the backlight module etc. to change the direction of propagation and polarization direction randomly, help thus to highlight simultaneously.

(13) circularly polarized light beam 5 of transmission changes linearly polarized light beam into by the quarter wave plate (not shown), thereby it can be used in LCD etc., and can not produce any absorption loss.In this manner, realized that by the polarization member of Fig. 1 focusing and brightness strengthen.

Then, illustrate that having of reflective polarizer select the reflection wavelength band.

Two-layer reflective polarizer according to the present invention has having of being same to each other or different to each other and selects the reflection wavelength band.For example, though one of reflective polarizer can reflect in whole visible light wavestrip, and another antireflection part has the reflection wavelength of selection band to overlap at least each other.The having of reflective polarizer select the reflection wavelength band for example can be with the use of polarization member and the type of element that will make up in using and light source corresponding and suitably design.Preferably, for example realize that with respect near the light beam that the 550nm wavelength, has high observability the reflection of selection is arranged.Particularly, the overlapping region of selecting the reflection wavelength band that has of two-layer reflective polarizer preferably includes the wavelength coverage of 540nm to 560nm.Under the situation of the reflective polarizer that comprises cholesteric liquid crystal compound as mentioned above, this has selects the reflection wavelength band clearly to determine according to the courage steroid chirality spacing of liquid crystal and refractive index; The centre wavelength that the reflection selected arranged is with formula (VIII) (λ=np) represent.

In addition, owing to need white light when the colored demonstration of needs, therefore further preferably these wavestrips have consistent characteristic in the visible light wavestrip, perhaps can cover the emitted spectral regions (435nm to 610nm in many cases) of light source at least.When consider for oblique incidence light beam cholesteryl liquid crystal have the reflection wavelength of selection spectrum to move to short wavelength side (blue shift) time, further preferably the overlay region covers the zone of wavelength greater than 610nm.Because this long wavelength side requires has and selects the reflection wavelength band significantly to depend on angle and wavelength from the incident beam of light source, therefore long wavelength's end at random is provided with corresponding to the specification that requires.For example, specifically in the backlight module that uses the wedge shape light guide plate in being usually used in LCD, the light that penetrates from light guide plate has the angle about 60 ° apart from normal direction.When incident angle became big, the amount of above-mentioned blue shift was tending towards increasing, and is about 100nm at about 60 ° angle place.Therefore, when the three-wavelength cold cathode ray tube is used for backlight module, and when red bright line spectrum (bright-line spectrum) when being 610nm, having the above-mentioned overlay region of selecting the reflection wavelength band to arrive more to approach wavelength is acceptable greater than the side of 710nm.In addition, from liquid crystal indicator etc. wherein colour developing resolution and the aspect of RGB, particularly preferably being and selecting the reflection wavelength band is to overlap each other in 380nm to the 780nm scope in whole visible wavelength range.

When the light time that backlight module is only launched specified wavelength,, also be enough for example iff covering obtainable bright line spectrum for the situation of using colored cold cathode ray tube.In addition, the light beam that penetrates when backlight module makes it when beginning to drop to a certain degree because of the design of lenticule, point and the prism of mobile object upper process (processed) is blocked along frontal, because can ignore the transmitted light beam with wide-angle incident, therefore not needing to have the reflection wavelength of selection to extend to long wavelength side.

Then, the length of delay that is used for retardation layer is described.

For reflective polarizer, the desirable length of delay R ' (referring to top formula (II)) of retardation layer vergence direction should be λ/2 (λ represents the incident light wavelength), thereby the light beam of retardation layer is passed in reflection fully, but in fact,, this value can not realize this purpose even not being accurate λ/2 yet.In addition, because vergence direction length of delay R ' changes because of incident angle, that is, this value generally is tending towards along with the increase of incident angle increasing, therefore for polarization is effectively changed, must come suitably definite this length of delay R ' by the angle of considering to reflect fully (entire reflection) etc.For example, for the reflection fully at the about 60 ° angle place of off-normal, this value should be configured such that the delay 60 ° of measurements is approximately λ/2.Have no particular limits for the method for adjusting vergence direction length of delay R ', can suitably adopt known method.For example, when retardation layer is biaxially-stretched film, can utilize ratio of elongation, film thickness etc. are adjusted.

In addition, because the birefringence of the reflective polarizer itself that works as the C-plate etc., the light beam that makes transmission cross reflective polarizer can change its polarization state.For example, the reflection circle polarizer that comprises cholesteric liquid crystal layers can have some character as the retardation layer of negative C-plate because of the distorted-structure of cholesteric liquid crystal compound.Therefore, the vergence direction length of delay R ' of retardation layer can be adjusted into less than λ/2 by the delay of considering reflective polarizer.Particularly, R ' should be λ/8 as formula (II) expression at least.The upper limit of R ' is not definite especially, can suitably be provided with it corresponding to purpose.As mentioned above, postponing R (referring to formula (I)) in the face is preferably littler.

Only for reference, Figure 10 shows the index ellipsoid that concerns between the optical anisotropy of the incident angle of clearly representing the C-plate and delay and C-plate.But this only is an example, does not therefore mean that restriction the present invention.Figure 10 shows at the birefringence resin to have the positive ≈ 0 of delay, tiltedly postpones example under the situation of biaxial orienting of=1/2 wavelength, in this case, obtains 1/2 wavelength in ± 40 degree positions.

As mentioned above, be not limited thereto about the embodiment that uses the reflection circle polarizer, but can make amendment in many aspects.For example, in the present invention, the C-plate that is used for retardation layer can be replaced by 1/2nd wavelength plates (being also referred to as the half-wavelength retardation plate).Promptly, polarization member of the present invention can comprise two-layer reflection circle polarizer at least and place half-wave plate between this two-layer reflection circle polarizer, wherein reflection circle polarizer layer has be used for that having of polarized light select reflection a plurality of the reflection wavelength of selection band is arranged, and these have the reflection wavelength of selection to overlap each other with bringing to small part.In this case, the sense of rotation of passing the circularly polarized light beam of each in the two-layer reflection circle polarizer is preferably opposite each other, and the vergence direction length of delay in the half-wave plate is desirably 0 or λ.When the vergence direction length of delay was set, the length of delay of reflection circle polarizer layer should be considered to be in the situation when using the C-plate.When using half-wave plate, the problem of anisotropy or colour developing may appear according to the position angle of sloping shaft.But for example, for each layer and the retardation layer of two-layer reflection circle polarizer, this colour developing can compensate by the layer that utilizes the wavelength diffusive property to differ from one another.

(second embodiment)

Below another embodiment of the present invention will be described.

In polarization member of the present invention, reflective polarizer can be the reflected ray polarizer.More specifically, polarization member of the present invention can comprise two-layer reflective polarizer at least and place middle layer between this two-layer reflective polarizer,

This two-layer reflective polarizer is a reflected ray polarizer layer, its selectively transmission one of intersect each other in the rectangular linearly polarized light, optionally reflect another simultaneously,

This two-layer reflected ray polarizer has be used for that having of polarized light select reflection a plurality of the reflection wavelength of selection band is arranged, and these wavelength bands overlap each other at least in part,

The middle layer comprises the stacked of single optical layers or at least two optical layers, and the middle layer has the function according to incident direction linearly polarized light beam of transmission incident when changing or not changing the polarization direction,

The angled placement of this two-layer reflected ray polarizer, so that have slow-axis direction in the face, be used for the light beam that transmission is included in incident ray polarized light and enters along the direction (normal direction) perpendicular to incidence surface, reflect the light beam that enters from vergence direction simultaneously effectively.

This polarization member for example can be by combined reflected linear polarizer and quarter wave plate (being also referred to as the quarter-wave retardation plate) to prepare the C-plate holder middle.More specifically, polarization member preferably comprises two-layer reflected ray polarizer at least, retardation layer and place two quarter wave plate layers between this two-layer reflected ray polarizer; One of them quarter wave plate is placed between a reflected ray polarizer layer and the retardation layer, and another quarter wave plate places between another reflected ray polarizer layer and the retardation layer; This two-layer reflected ray polarizer has be used for that having of polarized light select reflection a plurality of the reflection wavelength of selection band is arranged, these have the reflection wavelength of selection to overlap each other with bringing to small part, be positioned at lip-deep quarter wave plate of retardation layer and have a face slow axis, it becomes 40 ° to 50 ° angle with respect to the polarization axle that is placed on the reflected ray polarizer layer on retardation layer the same side; Be positioned at another lip-deep another quarter wave plate of retardation layer and have a face slow axis, it becomes-40 ° to-50 ° angle with respect to the polarization axle that is placed on the reflected ray polarizer layer on retardation layer the same side; Definite arbitrarily angle that forms by slow axis in the face of two-layer reflected ray polarizer.In this case, retardation layer must satisfy following formula (I) and (III).

R≤(λ/10) (I)

R’≥(λ/4) (III)

Illustrated above formula (I) and (III) in λ, the definition of R and R '.

Know that natural light can become circularly polarized light by the combination of linear polarizer and quarter wave plate.As shown in Figure 3, change the natural light beam 301 that enters linear polarizer 302 into linearly polarized light beam 303, the linearly polarized light beam 303 that further will pass quarter wave plate 304 changes circularly polarized light beam 305 into.Reflection circle polarizer layer and reflected ray polarizer layer be favourable based on comparing as the prism-type reflective polarizer of Brewster angle principle because it less relies on incident angle.

When by reflected ray polarizer layer simply with the C-plate holder during in the centre, about the optical axis of the light beam that enters the C-plate from vergence direction will with the direction of light beam always with right angle intersection, therefore expression does not postpone, and the deflection conversion can not occur.In this case, by quarter wave plate linearly polarized light beam is become circularly polarized light beam, the slow-axis direction of this quarter wave plate is 45 ° or-45 ° with respect to the polarization axle of reflected ray polarizer layer, subsequently, described linearly polarized light beam becomes the circularly polarized light beam of upset by the delay that utilizes the C-plate, becomes linearly polarized light beam once more by quarter wave plate then.

Have no particular limits according to quarter wave plate of the present invention and half-wave plate, and can suitably use any known plate.Concrete example comprises uniaxial tension or biaxial stretch-formed polymer film, the layer that forms by making liquid-crystal compounds hybrid orientation (hybrid aligning) (that is, in the in-plane uniaxial orientation, further being orientated at thickness direction) etc.Have no particular limits about the method that postpones in the face in control quarter wave plate and the half-wave plate, for example, can be by adjusting draw ratio, the polymer film of control stretching such as film thickness.

Be not particularly limited though can be used for the polymkeric substance of polymer film, its preferred example comprises: polyester polymer, as polyethylene terephthalate and PEN; Cellulosic polymer is as biacetyl cellulose and triacetyl cellulose; Acrylic acid series polymeric compounds is as polymethylmethacrylate; Styrenic polymer is as polystyrene and styrene-acrylonitrile copolymer (AS resin); Polycarbonate polymer is as the multipolymer of bisphenol-A and carbonic acid; Linearity or branched polyolefin, as tygon, polypropylene, and the rare multipolymer of ethene-third; The polyolefin that comprises ring structure is as polynorbornene; The polyvinyl chloride-base polymkeric substance; Acylamide polymer is as nylon and aromatic polyamide; The acid imide polymkeric substance; The sulfone base polymer; The polyether sulfone polymkeric substance; The polyetheretherketone compounds; The polyphenylene sulfide compounds; The vinyl alcohol compound; The vinylidene chloride base polymer; Ethene butyral base polymer; The arylide base polymer; The polyoxymethylene base polymer; And epoxide polymer.These polymkeric substance may be used singly or in combin.In addition,, for example provide ductility and retractable property, can in these polymeric materials, add proper additive for any purpose.

Similarly, the method for making polymer film has no particular limits, but can utilize the polymer film made by cast (extruding) and by making the polymeric material fusing, is configured as film and stretching and the polymer film made.See that from aspects such as physical strengths the latter's example is preferred.

Another example of polymer film is described in JP2001-343529A (WO01/37007).Material for polymer film, for example, can use resin composition, this resin composition comprises side chain and has the thermoplastic resin of replacement or unsubstituted one or more imides and the thermoplastic resin that side chain has replacement or unsubstituted one or more phenyl and one or more cyano group.This example is to have to comprise isobutylene and the alternating copolymer of N-methyl maleimide (N-methyl maleimide) and the resin composition of styrene acrylonitrile copolymer.

Similarly, reflected ray polarizer of the present invention has no particular limits, and can use known product.For example, specifically be can use to have optically anisotropic stretched film, its laminated product etc., the material of stretched film can with the materials similar of quarter wave plate and half-wave plate.

Fig. 4 is the synoptic diagram that the polarization member of this embodiment is shown, though present embodiment is not limited to this example.As shown in this Fig, this polarization member passes through stacked critical piece successively, be reflected ray polarizer 404 (can be referred to as hereinafter ' layer 4 '), quarter wave plate 405 (can be referred to as hereinafter ' layer 5 '), C-plate 406 (can be referred to as hereinafter ' layer 6 '), quarter wave plate 407 (can be referred to as hereinafter ' layer 7 ') and reflected ray polarizer 408 (can be referred to as hereinafter ' layer 8 ') and form, light beam enters from layer 4 one side.

Fig. 5 is the synoptic diagram that shows the angle of each the main element combination of polarization member be used for making Fig. 4.The angle that is formed by slow axis in the face of the polarization axle of linear polarizer 404 and quarter wave plate 405 is in 40 ° to 50 ° scope, and the angle that slow axis forms in the face of the polarization axle of linear polarizer 408 and quarter wave plate 407 is in-40 ° to-50 ° scope.In addition, the angle that forms about each element has no particular limits, even by any rotation set 1 (combination of linear polarizer 404 and quarter wave plate 405) with gather 2 (combinations of linear polarizer 408 and quarter wave plate 407) and also can obtain similar performance, keep above-mentioned angle simultaneously.For example, Figure 14 illustrates the example when gathering 2 half-twists as shown in Figures 4 and 5.Even this example can demonstrate performance just as shown in Figures 4 and 5.Because the C-plate does not have the optical axis in the face, therefore can arbitrary decision be used for the angle of combination.

Ideal operation principle when entering polarization member of the present invention with reference to figure 4 explanation light beams.

(1) at first, natural light beam 14 is from backlight module (light source) emission, so that vertically enter reflected ray polarizer 404 (layer 4).

(2) light beam 14 is divided into linearly polarized light beam 15 and linearly polarized light beam 16 with right angle intersection.Light beam 15 passes layer 4, light beam 16 reflections.

(3) linearly polarized light beam 15 passes quarter wave plate 405 (layer 5), and changes circularly polarized light beam 17 into.

(4) circularly polarized light beam 17 passes C-plate 406 (layer 6) becomes circularly polarized light beam 18, but does not change its polarization state.

(5) circularly polarized light beam 18 passes quarter wave plate 407 (layer 7), and changes linearly polarized light beam 19 into.

(6) linearly polarized light beam 19 passes C-plate 408 (layer 8) becomes linearly polarized light beam 20, but does not change its polarization state.

(7) linearly polarized light beam 20 accesss to plant (liquid crystal indicator etc.), and harmless lost territory transmission.

(8) except the natural light beam 14 from vertical direction, the natural light beam of launching from backlight module 21 enters layer 4 obliquely.

(9) light beam 21 is divided into linearly polarized light beam 22 and linearly polarized light beam 23 with right angle intersection.Light beam 22 passes layer 4 (reflected ray polarizer), with light beam 23 reflections.

(10) linearly polarized light beam 22 passes layer 5 (reflected ray polarizer) and changes circularly polarized light beam 24 into.

Experience the delay of 1/2 wavelength when (11) circularly polarized light beam 24 passes layer 6 (C-plate), thereby the upset sense of rotation becomes circularly polarized light beam 25.

(12) circularly polarized light beam 25 passes layer 7 (quarter wave plate) and changes linearly polarized light beam 26 into.

(13) linearly polarized light beam 26 is reflected by layer 8 (reflected ray polarizer) and becomes linearly polarized light beam 27.

(14) linearly polarized light beam 27 passes layer 7 (quarter wave plate) and changes circularly polarized light beam 28 into.

(15) delay of circularly polarized light beam 28 experience half-wave plate when passing layer 6 (C-plate), thus the upset sense of rotation becomes circularly polarized light beam 29.

(16) circularly polarized light beam 29 passes layer 5 (quarter wave plate), and changes linearly polarized light beam 30 into.

(17) linearly polarized light beam 30 passes layer 4 (reflected ray polarizer) becomes linearly polarized light beam 31, but does not change its polarization state.

(18) folded

light beam

16,23 and 31 turns back to backlight module one side and recycle.Re-circulation means is identical with the mechanism of first embodiment.

In this embodiment, the interior slow axis angulation of face of the polarization axle of reflected ray polarizer and quarter wave plate should be 45 ° and-45 ° in theory in ideal system among set 1 and 2 (Fig. 5).But, because the characteristic of reflective polarizer and wavelength plate is in fact also imperfect at visible-range, and has subtle change for each wavelength, therefore some problems as colour developing may appear.Problem as colour developing can solve by angle being changed certain number of degrees compensation tone, thereby reasonably optimizes total system.Owing to the other problems that descends as transmissivity when angle significantly departs from 45 ° or-45 °, can occur, therefore adjustment is restricted to ± 5 ° scope.

The preferable range that selection reflection wavelength band is arranged of reflected ray polarizer is similar to the reflection circle polarizer.Situation as the reflection circle polarizer, the wavelength properties of transmitted light beam moves towards short wavelength side with respect to the light beam with vergence direction incident, the long wavelength side that is preferably in outside the visible-range has enough polarization properties and delay property, thereby the reflected ray polarizer can be played a role fully for the light beam with wide-angle incident.

In addition, for the preferable range (formula (III)) of the vergence direction length of delay R ' in the retardation layer among this embodiment (C-plate), can be according to adjusting with the similar thought of using reflection circle polarizer situation.But, because comparing with the reflection circle polarizer, typical reflected ray polarizer itself has littler delay property, therefore the R ' of at least 1/8 wavelength is not enough, should be 1/4 wavelength or bigger.

In Figure 15, enter the situation of the polarizer of Figure 14 for the light beam of oblique incidence, by placing two quarter wave plates between the reflective polarizer, the variation of the polarization state that C-plate and another quarter wave plate cause is expressed on the Poincare spheroid.This illustrates the linearly polarized light beam that enters from first reflective polarizer and changes circularly polarized light beam and the linearly polarized light beam that changes upset into into.But this is the diagrammatic sketch that an example of the present invention is shown, and does not limit the present invention.

(the 3rd embodiment)

Another embodiment of various details.

In this embodiment, by meet at right angles or stacked abreast positive delay the (postponing in the face) for two biaxial film that λ/4, thickness direction retardation are at least λ/2 replace using the structure that forms by with the C-plate holder in the middle of two quarter wave plate layers, can obtain similar effects.In this case, Nz coefficient (thickness direction retardation/face in postpone) is 2 or can satisfies this requirement greatlyyer.

That is, polarization member of the present invention can comprise two-layer reflected ray polarizer at least and place two quarter wave plate layers between this two-layer reflected ray polarizer, wherein

This two-layer reflected ray polarizer has be used for that having of polarized light select reflection a plurality of the reflection wavelength of selection band is arranged, and these have the reflection wavelength of selection to overlap each other with bringing to small part,

Slow axis becomes 40 ° to 50 ° angle with respect to the polarization axle that is placed on the reflected ray polarizer layer on polarization member the same side in the face of a quarter wave plate,

Slow axis becomes-40 ° to-50 ° angle with respect to the polarization axle of the reflected ray polarizer layer on polarization member the same side in the face of another quarter wave plate,

Definite arbitrarily angle that forms by slow axis in the face of two quarter wave plate layers, and

The condition of formula (IV) below the quarter wave plate layer satisfies respectively:

Nz≥2.0 (IV)

Nz=(nx-nz)/(nx-ny) wherein.

In formula (IV), nx, ny and nz are respectively along the X-direction of principal axis in the quarter wave plate, the axial refractive index of Y-direction of principal axis and Z-, here, the X-direction of principal axis is the direction (slow-axis direction in the face) that shows largest refractive index in the quarter wave plate plane, and the Y-direction of principal axis is a direction (quick shaft direction in the face) vertical with the X-axle in the quarter wave plate plane, the Z-direction of principal axis is the thickness direction of quarter wave plate, and vertical with the Y-direction of principal axis with the X-direction of principal axis.

About the material of quarter wave plate and reflected ray polarizer layer, perhaps the method for delay and thickness direction retardation does not have concrete restriction in the chain of command, can use the description among second embodiment.

Fig. 6 is the synoptic diagram that the polarization member of this embodiment is shown, although present embodiment is not limited thereto.As shown in this Fig, this polarization member passes through stacked main element successively, be reflected ray polarizer 609 (can be referred to as hereinafter ' layer 9 '), quarter wave plate 610 (can be referred to as hereinafter ' layer 10 '), quarter wave plate 611 (can be referred to as hereinafter ' layer 11 '), reflected ray polarizer 612 (can be referred to as hereinafter ' layer 12 ') and form, light beam enters from layer 9 side.

Fig. 7 is the synoptic diagram that shows the angle of each the critical piece combination of polarization member be used for making Fig. 6.The angle that is formed by slow axis in the face of the polarization axle of linear polarizer 609 and quarter wave plate 610 is in 40 ° to 50 ° scope, and the angle that slow axis forms in the face of the polarization axle of linear polarizer 612 and quarter wave plate 611 is in-40 ° to-50 ° scope.In addition, the angle that forms for each element has no particular limits, even by any rotation set 1 (combination of linear polarizer 609 and quarter wave plate 610) with gather 2 (combinations of linear polarizer 612 and quarter wave plate 611) and also can obtain similar performance, keep above-mentioned angle simultaneously.For the convenience that illustrates, Fig. 6 and 7 illustrates the axle of the parallel and quarter wave plate layer of axle of upper and lower linear polarizer each other in the example of right angle intersection, but this embodiment is not restrictive.

Ideal operation principle during below by the polarization member that enters present embodiment with reference to figure 6 explanation light beams.

(1) at first, natural light beam 32 vertical incidence of launching from backlight module (light source).

(2) natural light beam 32 is divided into linearly polarized light beam 33 and linearly polarized light beam 34 with right angle intersection by layer 9 (reflected ray polarizer).Linearly polarized light beam 33 passes layer 9, with linearly polarized light beam 34 reflections.

(3) linearly polarized light beam 33 passes layer 10 and layer 11 (quarter wave plate).Because in example as shown in FIG., in the face of layer 10 in the face of slow axis and layer 11 slow axis intersect at a right angle, therefore when considering the combination of layer 10 and layer 11, the positive delay (delay in the face) is 0.Therefore, when passing layer 10 and 11 the time, linearly polarized light beam 33 becomes linearly polarized light beam 35, but does not change its polarization state.

(4) linearly polarized light beam 35 passes layer 12 (reflected ray polarizer), but does not change its polarization state, becomes linearly polarized light beam 36.

(5) linearly polarized light beam 36 is not transmitted to device (for example liquid crystal indicator) with losing.

(6) except the natural light beam 32 of vertical incidence, from natural light 37 oblique incidences of backlight module emission.

(7) natural light beam 37 is divided into linearly polarized light beam 38 and linearly polarized light beam 39 with right angle intersection by layer 9 (reflected ray polarizer).Linearly polarized light beam 38 passes layer 9, linearly polarized light beam 39 reflections.

(8) linearly polarized light beam 38 tilts to enter layer 10 and layer 11, and when pass these layers, under the influence of thickness direction retardation, and its 90 ° of polarization axis direction change and become linearly polarized light 40.

(9) linearly polarized light beam 40 enters layer 12 (reflected ray polarizer).

(10) since layer 12 have identical with layer 9 axially, so linearly polarized light beam 40 reflects by layer 12, becomes linearly polarized light beam 41.

(11) pass layer 10 and 11 the time when linearly polarized light beam 41, experience is by the influence of the delay described in top (9), so polarization axis direction changes 90 °, becomes linearly polarized light 42.

(12) linearly polarized light beam 42 passes layer 9 (reflected ray polarizer), but does not change its polarization state, becomes linearly polarized light beam 43.

(13) folded

light beam

34,39 and 43 turns back to backlight module one side and recycle.That describes among re-circulation means and first and second embodiment is identical.

The polarization member of this embodiment can show the polarization member similar performance with second embodiment.In addition, owing to omitted the C-plate, so the polarization member among this embodiment is better than the polarization member of second embodiment aspect production efficiency.Though have no particular limits for the quarter wave plate among this embodiment, for example can use a kind of above-mentioned quarter wave plate, but the film of more preferably biaxial stretch-formed polycarbonate (PC) and polyethylene terephthalate (PET), the perhaps layer of the liquid-crystal compounds of hydridization orientation.

Angular range about reflected ray polarizer and quarter wave plate formation can use foregoing description, can be according to adjusting slightly as the notion among second embodiment.

Similarly, select the reflection wavelength band, can use first and second embodiment about having of reflected ray polarizer.

In addition, in this embodiment, can change the service efficiency of oblique incidence light beam by the value (formula (IV)) that changes Nz.This preferable range has no particular limits, can be according to adjusting as the notion among first and second embodiment, to obtain the optimum efficiency that light utilizes.This embodiment is similar with the various embodiments described above of the delay that must consider reflective polarizer.

(the 4th embodiment)

Another embodiment of various details.

Can replace as obtaining similar effects by the structure that the C-plate holder is formed among second embodiment in the middle of two quarter wave plate layers as the biaxial film that λ/2, thickness direction retardation are at least λ/2 by using positive the delay (postponing in the face).In this case, the Nz coefficient is 1.5 or can satisfies this requirement greatlyyer.

That is, polarization member of the present invention can comprise two-layer reflected ray polarizer at least and place half-wave plate between this two-layer reflected ray polarizer, wherein

Slow axis becomes 40 ° to 50 ° angle with respect to the polarization axle of a reflected ray polarizer layer in the face of half-wave plate, and also becomes-40 ° to-50 ° angle with respect to the polarization axle of another reflected ray polarizer layer, and

Formula (V) below half-wave plate satisfies:

Nz≥1.5 (V)

Nz=(nx-nz)/(nx-ny) wherein.

In formula (V), nx, ny and nz are respectively along the X-direction of principal axis in the half-wave plate, the axial refractive index of Y-direction of principal axis and Z-, here, the X-direction of principal axis is the direction (slow-axis direction in the face) that shows largest refractive index in the half-wave plate plane, and the Y-direction of principal axis is a direction (quick shaft direction in the face) vertical with the X-direction of principal axis in the half-wave plate plane, the Z-direction of principal axis is the thickness direction of half-wave plate, and vertical with the Y-direction of principal axis with the X-direction of principal axis.

Do not have concrete restriction about material and the method for making reflected ray polarizer and wavelength plate, can use the explanation in preceding embodiment.

Fig. 8 is the synoptic diagram that the polarization member of this embodiment is shown, although present embodiment is not limited thereto.As shown in this Fig, this polarization member passes through stacked critical piece successively, be reflected ray polarizer 813 (can be referred to as hereinafter ' layer 13 '), half-wave plate 814 (can be referred to as hereinafter ' layer 14 '), reflected ray polarizer 815 (can be referred to as hereinafter ' layer 15 ') and form, light beam enters from layer 13 1 side.

Fig. 9 is the synoptic diagram that shows the angle of each the critical piece combination of polarization member be used for making Fig. 8.The angle that is formed by slow axis in the face of the polarization axle of linear polarizer 813 and half-wave plate 814 is in 40 ° to 50 ° scope, and the angle that is formed by slow axis in the face of the polarization axle of linear polarizer 815 and half-wave plate 814 is in-40 ° to-50 ° scope.Therefore, slow axis must be basically with right angle intersection in the face of two linear polarizer layers.

The polarization member of this embodiment can show the performance as the polarization member of the second and the 3rd embodiment, because the quantity of lamination reduces, therefore has superiority more aspect production efficiency.

Ideal operation principle when entering polarization member of the present invention with reference to figure 8 explanation nature light beams.

(1) at first, natural light beam 47 vertical incidence that penetrate from backlight module (light source).

(2) by layer 13 nature light beam 47 is divided into linearly polarized light beam 48 and linearly polarized light beam 49 with right angle intersection.Linearly polarized light beam 48 passes layer 13, and linearly polarized light beam 49 is reflected.

(3) pass layer during 14 (half-wave plate) when linearly polarized light beam, experience is positive to postpone the influence of (postponing in the face), therefore makes its polarization axis direction half-twist and becomes linearly polarized light 50.

(4) linearly polarized light beam 50 passes layer 15 (reflected ray polarizer), but does not change its polarization state, becomes linearly polarized light beam 51.

(5) the harmless lost territories of linearly polarized light beam 51 are transmitted to device (for example, liquid crystal indicator etc.).

(6) except the natural light beam 47 of vertical incidence, from natural light beam 52 incident obliquely of backlight module emission.

(7) by layer 13 nature light beam 52 (reflected ray polarizer) is divided into linearly polarized light beam 53 and linearly polarized light beam 54 with right angle intersection.Linearly polarized light beam 53 passes layer 13, linearly polarized light beam 54 reflections.

(8) linearly polarized light beam 53 tilts to enter layer 14 (half-wave plate), and passing layer 14 becomes linearly polarized light beam 55 and do not change its polarization axis direction.

(9) linearly polarized light beam 55 tegillums 15 (reflected ray polarizer) reflection, and become linearly polarized light beam 56.

(10) linearly polarized light beam 56 enters layer 14, does not pass with not changing its polarization axis direction, becomes linearly polarized light beam 57.

(11) linearly polarized light beam 57 passes layer 13 and does not change its polarization state, becomes linearly polarized light beam 58.

(12) folded

light beam

49,54 and 58 turns back to backlight module one side and recycle.Re-circulation means identical with described in preceding embodiment.

The angular range that is formed by reflected ray polarizer and half-wave plate as mentioned above.By the fine setting of the scope at reflected ray polarizer and angle that half-wave plate becomes can according to the second and the 3rd embodiment in identical thought carry out.

Similarly, select the reflection wavelength band, can use first to the 3rd embodiment about having of reflected ray polarizer.

In addition in this embodiment, change the service efficiency of oblique incidence light beam by the value (formula (V)) that changes Nz.Preferred range has no particular limits, and can adjust according to the thought identical with first to the 3rd embodiment, to obtain best optical efficiency.This embodiment is similar with the various embodiments described above of the delay that must consider reflective polarizer.

Though described the present invention about first to fourth embodiment above, the invention is not restricted to foregoing description, but can in the scope that does not break away from boundary of the present invention, carry out various modifications.For example, polarization member of the present invention can also be included in any other optical layers or any other element in the scope that realizes the object of the invention except aforesaid each element.

(manufacture method or the like)

Then, will describe and be used to method of making polarization member of the present invention etc.Be used to make the material of each element and method as mentioned above, described element such as C-plate, reflective polarizer and wavelength plate.

Have no particular limits though make the method for polarization member of the present invention, this polarization member can be by with above-mentioned each element and stacked manufacturing of any other element as required.Though the formation of lamination has no particular limits, and each element is merely able to stackedly, and from the aspect of availability and optical efficiency, these elements preferably come stacked by translucent bonding agent or pressure adhesive.Though there is not concrete difference between " bonding agent " and " pressure adhesive " in the present invention, for convenience's sake, will be than being easier to peel off and bonding once more bonding agent is called " pressure adhesive ".

From suppressing the aspect of surface reflection etc., though have no particular limits, bonding agent or pressure adhesive preferably transparent and in visible-range, do not absorb, refractive index is as far as possible near the refractive index of each layer.Therefore, for example preferably use based on acrylic acid the bonding agent or the pressure adhesive of epoxy and isocyanate material.These suitably used bonding agents or pressure adhesive can be solvent-borne types, perhaps for example are the polymerizable ultraviolet types, hot polymerization mould assembly, two liquid mixture types or the like.The method of stacked each element can suitably be selected according to characteristic, without any special restriction.For example, can utilize stacked in certain sequence these layers of method that on oriented layer etc., form single domain respectively and send it to translucent base.

For example,, can also suitably form oriented layer and wait the layer that replaces using bonding agent or pressure adhesive, and can directly form each element (being called ' directly and coating continuously ') according to a definite sequence when each element is when layer of containing liquid-crystal compounds.This method is favourable from the aspect that reduces polarization member thickness for example.When using reflection circle polarizer and C-plate, because each element does not planar have optical axis, and owing to can determine arbitrarily in conjunction with the angle, therefore in manufacture process, can use by scroll bar formula (roll-to-roll) process and the above-mentioned combination that directly applies continuously, thereby boost productivity.

Each element and bond layer (pressure-sensitive adhesive layer) may further include various bonding agents or the like as required.For example, can add the particulate that is used for the diffusivity adjustment, in order to the isotropy chromatic dispersion to be provided, perhaps can suitably add surfactant etc., when film forms in order to levelability (leveling property) to be provided.In addition, can suitably add ultraviolet light absorber or antioxidant etc.

(polarized light source and image display device)

The polarized light source and the image display device that utilize polarization member of the present invention will be described below.

Polarized light source of the present invention (polarized light source apparatus) comprises light source, reflection horizon and polarization member of the present invention, and this polarization member is stacked on the light source through the reflection horizon.Have no particular limits though be used to make the method for polarized light source, for example can use the method described in JPH10 (1998)-321025A.

In addition, image display device of the present invention is a kind of image display device that comprises polarization member of the present invention.Though utilize the image display device of polarization member of the present invention or polarized light source to be preferably used for as organic EL display without any special restriction, the image display device of PDP and CRT, it particularly preferably is used for LCD device.

LCD device of the present invention is described below.

LCD device of the present invention comprises polarized light source of the present invention, and liquid crystal cell (cell) further is stacked on the polarized light source.Method about element and manufacturing LCD device of the present invention has no particular limits, and can suitably use known elements and manufacture method.Polarized light source of the present invention has fabulous optical efficiency, and therefore the bright light that can provide has fabulous emission light verticality, and does not have brightness irregularities.In addition, the scale of polarized light source can be enlarged (upsize).Therefore, polarized light source can be preferably used as backlight module system in the formation of various LCD device, especially, is preferred for the direct view liquid crystal device.

About being used in the liquid crystal cell in the LCD device of the present invention, can use any suitable liquid crystal cell and without any special restriction.The light beam that is polarization state is entered so that the liquid crystal cell of demonstration to be provided.For example, preferably use the liquid crystal cell of twisted nematic liquid crystal or STN Super TN liquid crystal.But, be not limited to these examples, utilize the non-liquid crystal that reverses, have visitor-main classes (guest-host base) liquid crystal that is dispersed in the dichroic dyestuff in the liquid crystal, the liquid crystal cell of ferroelectric liquid crystals etc. is fit to equally.Similarly, have no particular limits about the system that drives liquid crystal.

About having no particular limits, can suitably use the well known elements of LCD device with liquid crystal cell element in addition.For example, suitable optical layers can arrange suitably that these optical layers comprise diffusing panel; antiglare layer, anti-reflective film, protective seam; fender, above any all will placing on the polarization plates of observing side, optical layers also comprises the compensating delay plate that places between liquid crystal cell and the polarization plates.

Then, Organnic electroluminescent device (organic EL display) will be described below.

Though polarization member of the present invention and polarized light source can be used for the various image display devices outside the LCD device, they are suitable for for example organic EL display.About organic EL display of the present invention, except using polarization member of the present invention or polarized light source, be not particularly limited, can use known structure and manufacture method.Following explanation about organic EL display is not in order to limit the present invention.

In general, organic EL display has a luminophor (organic electroluminescent body), and this luminophor is made by stacked in certain sequence transparency electrode, organic luminorphor layer and metal electrode on transparent substrates.Here, the organic luminorphor layer is the laminated body of various organic films.Its known example comprises the hole injection layer made by one or more triphenylamine derivatives etc. and the lamination of the emitter made such as the fluorescence organic solid of anthracene; The lamination of emitter and the electron injecting layer made by perylene derivant etc.; Perhaps hole injection layer, the lamination of emitter and electron injecting layer.

In general, the principle that organic EL display injects the system of organic emitter according to applying voltage to transparency electrode and metal electrode so that with hole and electronics is launched light, by these holes and electronics again in conjunction with the energy excitation fluorescent material that produces, the fluorescent material of being excited is launched light when returning its ground state.The mechanism of combination and general-purpose diode similar again in this process.This means that electric current and light emissive porwer show sizable non-linear with rectification with respect to institute's making alive.

For organic EL display, preferably at least one electrode is transparent, so that obtain the luminous of organic luminorphor layer.In general, the transparency electrode with transparent conductive material such as tin indium oxide (ITO) is used as anode.It is effectively for promoting electronics to inject and improving luminescence efficiency thus that anticathode uses the material with less work content, in general, can use the metal electrode as Mg-Ag and Al-Li.

In the organic EL display of structure as mentioned above, the organic luminorphor layer is made by the film as thin as a wafer such as about 10nm.Therefore, the organic luminorphor layer basically can all light of transmission as transparency electrode.Therefore, when this layer does not illuminate, before by metal layer reflection, penetrate the surface that arrives transparent substrates once more from transparent substrates surface and the incident light that passes transparency electrode and organic luminorphor layer.Look like mirror when therefore, the display surface of organic EL display is from visual observation.

As mentioned above, typical organic EL display has radiative organic luminorphor layer when applying voltage, and this organic luminorphor layer has transparency electrode in face side, has metal electrode at the rear portion.With the organic luminorphor layer, transparency electrode and metal electrode combination are to be formed with dynamo-electric luminophor.In this organic EL display, polarization plates can be placed the face side of transparency electrode, simultaneously, retardation plate can be placed between transparency electrode and the polarization plates.

Retardation plate and polarization plates have played inclined to one side effect to incident from the outside and by the light of metal electrode reflection, and this polarization has the effect that can not observe the mirror of metal electrode from the outside thus.Especially the mirror of this metal electrode can be blocked through the following steps fully, promptly forms retardation plate with quarter wave plate and is π/4 with the angular setting that the polarization direction of retardation plate and polarization plates forms.

That is, polarization plates only transmission enter linearly polarized light composition in the ambient light of organic EL display.In general, linearly polarized light becomes elliptically polarized light by polarization plates.When retardation plate is quarter wave plate, and when the polarization direction of polarization plates and retardation plate angulation was π/4, light became circularly polarized light.

Usually, this circularly polarized light passes transparent substrates, transparency electrode and organic film.After the metal electrode reflection, light passes organic film once more, transparency electrode and transparent substrates, and the place becomes linearly polarized light at retardation plate.In addition, because the polarization direction of linearly polarized light and polarization plates meets at right angle, therefore can not pass polarization plates.Therefore, the mirror of metal electrode is blocked fully.

Though polarized light source and the image display device that utilizes polarization member of the present invention described above the invention is not restricted to foregoing description.The polarization member of the present invention that the reflective polarizer of requirement of the present invention and retardation layer are satisfied in utilization can show the effect that transmission frontal light only reflects and eliminate the light of vergence direction simultaneously.In addition, the reflection wavelength of selection band arranged, can in having the wide wavelength coverage of less wavelength dependency, show these effects by what adjust reflective polarizer.In addition, owing to as conventional technology in the combined interference optical filter compare with focusing system with the parallelization that the bright line transmitting illuminant provides, the dependence of light source characteristic is reduced, so it can be used for various polarized light sources and image display device.

(example)

Be to further specifying that the present invention did below with reference to example and comparative example.Should be noted that the present invention is not limited only to these examples.

(instrument)

Equipment used in these examples and comparative example is described below.Cold cathode ray tube (CCFL) is the product of Elevam company.Backlight module is the product of Stanley Electric Applicance Co., Ltd and Tama Electric Applicance Co., Ltd, and light table is the product of HAKUBA.

Used measurement mechanism is as follows.

(1) to select the reflection wavelength band in order having measured, to use instantaneous multichannel photometric system (trade name :) by the MCPD 2000 of Otsuka Electron equipment Co., Ltd production.

(2) measure for turbidity, use nephelometer (trade name :) by the HM 150 of Murakami colored research laboratory production.

(3), use spectrophotometer (trade name :) by the U4100 of Hitachi company limited production for the measurement of transmission/spectrum of reflected light characteristic.

(4), use the DOT3 (trade name) that produces by the colored research laboratory of Murakami for the feature measurement of polarization plates.

(5), use birefringence measurement device (trade name: the KOBRA21D that produces by the Oji scientific instrument) for the measurement of the delay of retardation plate etc.

(6), use brightness photometer (trade name :) by the BM7 of Topcon company production for brightness measurement.

(example 1)

Manufacturing as described below comprises the polarization member of reflection circle polarizer and negative C-plate, and measurement characteristics.

At first, by utilizing obtainable polymerizable nematic crystal polymkeric substance on the market (polymerizable liquid-crvstalline unit compound) and chiral reagent manufacturing to comprise the reflective polarizer (reflection circle polarizer) of cholesteric liquid crystal layers.Determining type and mixing ratio, is that 550nm, width are approximately having of 60nm and select the reflection wavelength band thereby make the cholesteric liquid crystal layers that obtains like this have central value.Particularly, the LC242 (trade name) that BASF is produced is used for polymerizable liquid-crvstalline unit compound, and the LC756 (trade name) of BASF production is used for polymerizable chiral reagent, and mixing ratio is as follows.

Liquid crystal cell compound: chiral reagent=4.9: 95.1 (weight ratio)

Particularly, the reflection circle polarizer is by following operation manufacturing.At first, the potpourri of polymerizable chiral reagent and polymerizable liquid-crvstalline unit compound is dissolved in cyclopentane, be adjusted into solute density (solute consistency) then with 20wt%.The initiating reagent (initiating reagent) (trade name: by the Irg907 of Ciba-Geigy company limited production) of 1wt% is added in this solution, thus the preparation coating solution.

Preparation has the thick PET film of 75 μ m (trade name: by the industrial Lumirror of Toray), in order to be orientated, its surface is handled with friction fabric, and the orientation substrate is provided thus.Then, on the treatment surface of orientation substrate, by using wire bar applying coating solution.Simultaneously, adjust the amount of solution, making coating thickness is 5 μ m after drying.Then 90 ℃ of dryings 2 minutes, further once be heated to 130 ℃ as liquid crystal isotropic transition temperature, then the slow state of orientation of cooling to be consistent.By at 80 ℃ of (10mW/cm ²* 1min) utilize the ultraviolet ray irradiation that it is solidified, obtain comprising the reflective polarizer A of cholesteric liquid crystal compound.The preparation glass plate, on this glass plate, apply translucent isocyanic acid salt bonding agent (trade name :) by the AD249 of Tokushiki company limited production, to have the thickness of 5 μ m, above reflective polarizer A transfers to, thereby obtain required reflection circle polarizer.In measurement, what this reflection circle polarizer had the 520nm to 580nm that designed has the reflection wavelength of a selection band.

Then, manufacturing comprises the negative C-plate of polymerisable liquid crystal compound, thereby cholesteric is had selecting the central value of reflection wavelength band is 350nm.Particularly, the LC242 (trade name) of BASF production and the LC756 (trade name) of BASF production are used for polymerizable liquid-crvstalline unit's compound and polymerizable chiral reagent, mixing ratio is as follows.

Liquid crystal cell compound: chiral reagent=11.0: 88.0 (weight ratio)

Particularly, negative C-plate is by following operation manufacturing.At first, the potpourri of polymerizable chiral reagent and polymerizable liquid-crvstalline unit compound is dissolved in cyclopentane, be adjusted into solute density then with 30wt%.The initiating reagent (trade name: by the Irg907 of Ciba-Geigy company limited production) of 1wt% and the activating agent (trade name: by the BYK-361 of BYK-Chemie Japan production) that shows of 0.013wt% are added in this solution.

Preparation has the thick PET film of 75 μ m (trade name: by the industrial Lumirror of Toray), in order to be orientated its surface is handled with friction fabric, and the orientation substrate is provided thus.Then, on the treatment surface of orientation substrate, by using wire bar applying coating solution.Simultaneously, adjust the amount of solution, making coating thickness is 6 μ m after drying.Then 90 ℃ of dryings 2 minutes, further once be heated to 130 ℃ as liquid crystal isotropic transition temperature, then the slow state of orientation of cooling to be consistent.By at 80 ℃ of (10mW/cm ²* 1min) utilize the ultraviolet ray irradiation that it is solidified, obtain comprising cholesteryl liquid crystal and the lamination of the required negative C-plate that in the orientation substrate, forms.

In measurement, this negative C-plate has delay (can think 0 basically) along frontal 2nm for the light beam with 550nm wavelength.This delay is 160nm (＞λ/8) along the direction of 30 ° of inclinations.

Thus obtained reflection circle polarizer and negative C-plate are used to make polarization member.At first, preparation is included in the reflection circle polarizer that forms reflection circle polarizer A on the glass plate.Then, will bear the C-plate and transfer to reflection circle polarizer A.More specifically, apply translucent bonding agent (trade name :), go up the negative C-plate that forms in orientation substrate (PET film) and be adhered to this reflection circle polarizer A on reflection circle polarizer A, to have the thickness of 5 μ m by the AD249 of Tokushiki company limited production.Then, will be orientated substrate and peel off, only stay negative C-plate.Further in an identical manner another reflection circle polarizer A is transferred on the negative C-plate, obtain required polarization member thus.This polarization member comprises the first reflection circle polarizer A that is stacked in successively on the glass plate, the negative C-plate and the second reflection circle polarizer A, and each layer is bonding by bond layer.

Then, estimate the performance of resultant polarization member.At first, this polarization member combines with the green diffused light source of bright line spectrum at 544nm, so that make polarized light source.Particularly, G0 type cold cathode ray tube that Elevam company is produced and light diffuser plate (turbidity: at least 90%) are in conjunction with to provide diffused light source, polarization member further combines with this diffused light source so that polarized light source to be provided, and light source is placed straight-down negative (direct-type) back light module device inside.Light diffusing board places between polarization member and the cold cathode ray tube.

In the inspection of the characteristic of polarized light source, light beam penetrates along normal direction, but when the oblique angle be 30 ° or when bigger transmitted light beam reduce, when the oblique angle is approximately 45 °, do not have the light beam ejaculation basically.Figure 16 illustrate for only use diffused light source and in conjunction with the polarization member of this example with the relation between emission angle and the relative brightness under any situation that polarized light source is provided.

The polarization member that Figure 16 illustrates this example can focus on light beam along frontal effectively.This can think a characteristic of polarization member, because it has been generally acknowledged that in direct type backlight module and to be difficult to scioptics or prism focuses on light beam along frontal, unlike the situation of side light type backlight module.

Then, the polarization member of this example is placed on the backlight module that comprises the three-wavelength cold cathode ray tube (sidelight-wedge type backlight module of being produced by Stanley Electric Applicance Co., Ltd), and be used for LCD device, estimate its characteristic thus.Similarly, in this case, light beam penetrates along normal direction, but when the oblique angle be 30 ° or transmitted light beam minimizing when bigger.Because polarization member is not corresponding with whole visible-range, because the incomplete contraction (stop-down) of angle, institute still can eliminate and has the green spectral (545nm) of high observability so that the light beam of blue (435nm) and redness (610nm) leaked.Therefore, the effect as focalizer is confirmed.

(example 2)

Except using positive C-plate to replace the negative C-plate, make polarization member according to the mode identical with example 1.At first, make the positive C-plate that contains the polymerisable liquid crystal compound by using by the liquid crystal monomer (being called polymerisable nematic monomer A) of following chemical formulation.

The concrete operations of making positive C-plate are as follows.At first, polymerization nematic monomer A is dissolved in cyclopentane, and be adjusted into solute density with 30wt%.In addition, the initiating reagent (trade name: by the Irg907 of Ciba-Geigy company limited production) with 1wt% adds in this solution so that coating solution to be provided.Preparation PET film (trade name: by the industrial Lumirror of Toray, thickness: 75 μ m), on this film, form the shallow layer of the cyclohexane solution (0.1wt%) of separant (release agent) (octadecyl trimethoxy silane (octadecyl trimethoxysilane)), be dried the formation vertical alignment layer then, form the orientation substrate thus.On the surface of the orientation substrate that forms vertical alignment layer, apply above-mentioned coating solution by using wire bar.Simultaneously, adjust the amount of solution, making film thickness is 2 μ m after drying.Then with it 90 ℃ of dryings 2 minutes, once be heated to 130 ℃ as liquid crystal isotropic transition point, then the slow state of orientation of cooling to be consistent.Then, by at 80 ℃ of (10mW/cm ²* 1min) utilize the ultraviolet ray irradiation that it is solidified, form lamination thus with the required positive C-plate that in the orientation substrate, forms.In measurement, for the light beam with 550nm wavelength, the delay of this positive C-plate is 0 on frontal, and this delay is approximately 170nm (＞λ/8) in the measurement of 30 ° of inclinations.

Except using positive C-plate to replace the negative C-plate in the example 1, obtain a kind of polarization member according to the mode identical with example 1.In by the assessment that utilizes the polarization member of acquisition as in the example 1, identical with example 1 basically about the result of performance.

(example 3)

Manufacturing is described below comprises the reflected ray polarizer, the polarization member of quarter wave plate and C-plate, and assess its performance.

At first, make the reflected ray polarizer.Promptly, PEN (PEN) and naphthalene dicarboxylic acids-terephthalic acid (TPA) copolyester (co-PEN) (naphthalene dicarboxylicacid-terephthalic acid copolyester) is alternately stacked, adjust film thickness by presenting-hinder (feed-block) method simultaneously, obtain 20 layers multilayer film thus.This multilayer film of uniaxial tension then.When stretching, temperature is about 140 ℃, is approximately 3 along the draw ratio of TD direction.In the stretched film that obtains like this, each film has the thickness of about 0.1 μ m.Thisly comprise that 20 layers the laminate film of film is stacked with five, comprise 100 layers product altogether, obtain required reflected ray polarizer (reflective polarizer B) thus thereby provide.Because whole reflection potentiales, reflective polarizer B has reflection function for the linearly polarized light that is not less than 500nm and be not more than in the wavelength band of 600nm.

In addition, utilize reflective polarizer B to make polarization member.Promptly, the quarter wave plate that the monadic stretching membrane of polycarbonate is made (trade name: the NRF film of producing by Nitto Denko company, the delay (in the face postpone) that has 135nm at the 550nm place) is adhered to two surfaces of the negative C-plate of in example 1, making, and, reflective polarizer B is adhered to the surface of outermost, to obtain required polarization member.Slow-axis direction is 45 ° at light incident side in the face of quarter wave plate thereby each layer combination made, the C-plate is not axially, slow-axis direction is-45 ° in exiting side in the face of quarter wave plate, and when the transmission-polarizing of reflective polarizer B axially when light incident side is 0 °, axially be 90 ° at the transmission-polarizing of exiting side polarizer.Each layer comes bondingly by applying the thick acrylic pressure sensitive bonding agent of 25 μ m (No.7 that is produced by Nitto Denko company), and will be orientated substrate in order only to utilize the layer that contains liquid crystal and peel off from bearing the C-plate.In assessment, use thus obtained polarization member according to the mode substantially the same with example 1, it shows the performance substantially the same with example 1.

(example 4)

Manufacturing is described below comprises the polarization member of reflected ray polarizer and half-wave plate, and assess its performance.At first, make two reflected ray polarizer B according to the mode identical with example 3, and preparation phase shift films (half-wave plate), this phase shift films obtains by biaxial stretch-formed polycarbonate membrane (being produced by KANEKA company), and has the front delay (wavelength of measurement: 550nm) with the Nz coefficient with 2.0 of 270nm.Then, half-wave plate is clipped in the middle of two reflective polarizer B, thus bonding these layers and obtain required polarization member.About each layer in conjunction with the angle, when the transmission-polarizing of reflective polarizer B axially when light incident side is 0 °, slow-axis direction is 45 ° in the face of half-wave plate, the transmission-polarizing of polarizer is 90 ° in exiting side axially.(by the No.7 of Nitto Denko company production) comes bonding each layer to have the thick acrylic pressure sensitive bonding agent of 25 μ m between each layer by applying.In the assessment that is similar to example 3, find that this polarization member has substantially the same performance with polarization member in the example 3.

(example 5)

Describe below and be manufactured on the reflection circle polarizer (broadband reflection circle polarizer) that wide wavelength zone has selection reflection wavelength band.This reflection circle polarizer uses with the manufacturing polarization member with the C-plate, and assesses its performance.

At first, make broadband reflection circle polarizer.That is, prepare nematic monomer A (as mentioned above) and the chiral monomer B that represents by following structural formula.

The nematic monomer A

Chiral monomer B

Then, nematic monomer A and chiral monomer B are mixed and polymerization with predetermined ratio, be used to make cholesteric liquid crystal layers.In addition, have various four cholesteric liquid crystal layers selecting the reflection wavelength band that have by changing the mixing ratio of nematic monomer A and chiral monomer B, can producing.In the mill, with reference to EP application 0834754.Specify as follows.

Below table 1 ratio that is used to mix nematic monomer A and chiral monomer B is shown, and having of each the reflective cholesteric layer that calculates thus selected reflection wavelength band and centre wavelength.

(table 1)

Then, with nematic monomer A and chiral monomer B polymerization with synthetic cholesteric liquid crystal compound.That is to say that every kind of potpourri of component as shown in table 1 is dissolved in the tetrahydrofuran solution with preparation 33wt%, further add the initiating reagent (azoisobutyronitrile) of 0.5wt%.

This solution is carried out nitrogen purge (nitrogen-purge) at 60 ℃, then with common mode polymerization.The product of Huo Deing is with diethyl ether precipitate and separate and carry out refining to obtain required cholesteric liquid crystal compound more like this.

Prepare thick Triafol T (TAC) film of 80 μ m (trade name :) by the TD-TAC of Fuji photographic film company limited production, apply the thick polyimide layer of about 0.1 μ m thereon, rub this polyimide laminar surface so that the orientation substrate to be provided with artificial fibre frictoin fabric.Then, on this friction surface, apply the 10wt% dichloromethane solution of cholesteric liquid crystal compound by using wire bar, thereby make the coat film drying have the thickness of 1.5 μ m afterwards.It 140 ℃ of heating 15 minutes, is at room temperature kept subsequently and cool off,, obtain cholesteric liquid crystal layers thus so that the state of orientation of cholesteric liquid crystal compound is fixed.Each synthetic like this cholesteric liquid crystal compound is all carried out aforesaid operations, to obtain the having cholesteric liquid crystal layers of selecting the reflection wavelength band that has as shown in table 1 respectively.

Four cholesteric liquid crystal layers of Huo Deing are bonding from short wavelength side in a certain order like this, to obtain the having thick liquid crystal combination layer of about 10 μ m, form required broadband reflection circle polarizer thus.By on the surface of each liquid crystal layer, applying transparent isocyanic acid salt bonding agent (trade name: the AD244 that produces by Tokushiki company limited) carry out bondingly, peel off the alignment surfaces (TAC film) of a side subsequently.In measurement, the broadband reflection circle polarizer of Huo Deing has and in 430nm to 710nm scope the selection reflection function is arranged like this.

The C-plate is made according to the mode identical with example 1, broadband reflection circle polarizer is bonded on two surfaces, thereby obtains required polarization member.About adhering to, the transparent pressure sensitive bonding agent that 25 μ m are thick (by the No.7 of Nitto Denko company production) is coated between each layer, carries out as the operation in the example 1.Upper and lower reflection circle polarizer is set, thereby makes transmission (reflection) circularly polarized light by identical direction rotation.

Then, as in the example 1, evaluate the performance of polarization member in this example.In the assessment that utilizes green diffused light source, confirm that focusing performance is similar to the focusing performance of polarization member in the example 1.Be used for having the assessment of backlight module of the liquid crystal indicator of three-wavelength cold cathode ray tube in utilization, the same good in the focusing performance among this embodiment and the example 1.It is fabulous that the polarization member of this example is compared with example 1, and it shows the focusing performance of same degree at whole visible region.

In addition, the polarization member of this example is placed on another backlight module (utilize the direct type backlight module of cold cathode ray tube, produced by Tama Electric Applicance Co., Ltd), and assess its focusing performance.Similarly, in this case, light beam penetrates along normal direction, but when the oblique angle be 30 ° or when bigger, the transmitted light beam minimizing.Therefore, demonstrate similar focusing performance at whole visible region.

(example 6)

Make polarization member according to the mode identical with example 5, except changing the thickness and the length of delay of C-plate, focusing performance in the example 5 assessment.In the measurement of this example, the C-plate has the thickness of 4 μ m, positive postpones to be 1nm, is 100nm (＞λ/8) in the delay of 30 ° of inclinations.

Figure 17 illustrates for the emission angle of outgoing beam and the relation between the relative brightness under following two kinds of situations, described situation is for utilizing by each polarization member in example 5 sons and 6 being combined the situation of the polarized light source for preparing with diffused light source, and the situation of only using diffused light source.The figure shows, though arbitrary polarization member shows fabulous focusing performance, the polarization member of example 5 has more sharp-pointed focusing angle and bigger increase aspect front face brightness.

(example 7)

The polarization member of example 5 is assemblied in the LCD device, and assesses this display performance.Specifically describe as follows.At first, for LCD device, the TFT LCD device (diagonal line: 11.3 inches) that the Dynabook SS3430 (trade name) that preparation is produced by Toshiba company obtains.This device utilizes the light source of side light type leaded light, focuses of the light beam into the front by means of prismatic lens.Then, prismatic lens is removed from this LCD device, with quarter wave plate (trade name: the NRF-140 that produces by Nitto Denko company) with respect on the polarization axle polarizer that is adhered to this device rear portion at 45, in addition, the polarization member that obtains in the example 5 is adhered on the surface.About adhering to, use the thick translucent pressure adhesive of 25 μ m (by the No.7 of Nitto Denko company production).In this manner, can handle the LCD device that can get on the market, to obtain required LCD device, wherein the polarization member with example 5 is assembled in this device.The LCD device that obtains like this with polarization member and utilize between the untreated LCD device of prismatic lens performance relatively in, the character that is used for focusing on towards the front is substantially equal to utilize the display equipment of prismatic lens, and front face brightness has increased by 20% after handling.This result shows that polarization member of the present invention is better than conventional technology, as prismatic lens.

(comparative example 1)

Except with two-layer reflection circle polarizer each other directly in conjunction with and do not use the C-plate, make polarization member according to the mode identical with example 1.In the assessment of the performance of this polarization member, optical function is restricted to and the identical rank of individual reflection circuit polarizer layer, can not observe simultaneously if any selecting reflectance to increase, and the phenomenon that descends of transmissivity along inclined direction.

(comparative example 2)

Except utilizing quarter wave plate to come replaced C-plate, make polarization member according to the mode identical with example 1.Used quarter wave plate is that to be postponed by the front be the A-plate (trade name: by the NRF-140 film that Nitto Denko company produces, thickness: 50 μ m) that the stretching polycarbonate membrane of λ/4 and Nz coefficient=1.0 is made.In assessment, compare positive transmission with example 1 and reduce about 1/2 the polarization member of such acquisition.In addition, can not reduce along the transmission of oblique incidence direction, polarization member can not show and focus on and the parallel light function.

(comparative example 3)

Obtain polarization member according to the mode identical, absorb dichroic polarizer (trade name: the NPF-EG1425DU that produces by Nitto Denko company) replace reflective polarizer B except using the iodine class that can obtain on the market with example 3.In the assessment of this polarization member, owing to obtain limiting the effect of angle of visibility (visibility angle) along frontal transmission performance and absorption characteristic along inclined direction, but because significant absorption loss makes not raising of front face brightness.

(by utilizing the brightness assessment of light table)

Each polarization member among example 1-6 and the comparative example 1-3 is placed the available light table (product of HAKUBA on the market, the three-wavelength fluorescent light, the straight-down negative diffused light source) on, the brightness of vertical uplift (2 ° angle of visibilities) is measured by utilizing brightness photometer (trade name: by the BM7 of Topcon company production).Be set to 100 by the value of only utilizing light table to record and make the measured value standardization.Measurement result is shown in Figure 2.

(table 2)

Relative brightness

Example 1 80

Example 2 78

Example 3 72

Example 4 70

Example 5 82

Example 6 90

Comparative example 1 67

Comparative example 2 21

Comparative example 3 39

As shown in table 2, even when being used for light table, the polarization member of each example shows along the fabulous brightness of frontal and strengthens effect.As shown in Figure 16 and 17, though for the direct type backlight module that is used for LCD device, the positive relative brightness of polarization member in use surpasses 100 (front face brightness of initial backlight module) in each example, but relative brightness is lower than 100 slightly in table 2, because for available light table on this market, compare with the situation of using direct type backlight module, the efficient of the light beam that is returned along normal direction by reflective polariser reflects is low slightly.However, table 2 illustrates with the polarization member in each comparative example and compares, and the polarization member of each example has good especially effect in enhancing along aspect the brightness of frontal.

Industrial applicibility

As mentioned above, polarization member of the present invention can be towards the light of light source usable reflection inclination transmission Bundle, and can not be reduced to transmission-polarization properties that front face brightness is made the vertical incidence light beam of contribution. In addition, can be by changing towards the inclination transmitted light beam (that is, reflect polarized light) of light source reflection For the light beam that can do for strengthening front face brightness contribution further highlights. And, by That adjusts reflective polarizer has the reflection wavelength of a selection band, can have dependent than small wavelength Show these effects in the wide wave-length coverage. In addition, since with routine techniques in combined interference filter The parallel light that mating plate provides with the bright line spectrum light source is compared with focusing system etc., and is of the present invention Therefore the less characteristic that depends on light source of polarization member can be used for various polarized light sources and image Display unit. For example, when being used as the polarizer of liquid crystal display component backlight module side, can Show with the brightness that obtains fabulous observability. In addition, because the diffused light tool that utilizes light source to penetrate Excellent efficiency is arranged, therefore can be used in and form the high brightness polarized light source apparatus, and as organic The EL display unit, the image display device of PDP and CRT.

Claims

1. a polarization member wherein comprises two-layer reflected ray polarizer at least, and places retardation layer and two quarter wave plate layers between this two-layer reflected ray polarizer,

One of described quarter wave plate layer places between one of described reflected ray polarizer layer and the described retardation layer, and another described quarter wave plate is placed between another described reflected ray polarizer layer and the described retardation layer,

Described two-layer reflected ray polarizer has a plurality of selective reflecting wavelength bands of the selective reflecting that is used for polarized light, and described selective reflecting wavelength band overlaps each other at least in part,

Be positioned at the quarter wave plate layer of one face side of this retardation layer, slow axis becomes 40 ° to 50 ° angle with respect to the polarization axle of the reflected ray polarizer layer that is positioned at the same side in its face,

Be positioned at another the quarter wave plate layer of face side of this retardation layer, slow axis becomes-40 ° to-50 ° angle with respect to the polarization axle of the reflected ray polarizer layer that is positioned at the same side in its face,

Definite arbitrarily angle that forms by slow axis in the face of described two quarter wave plate layers, and

Formula I below described retardation layer satisfies and the condition of III:

R≤λ/10 I

R’≥λ/4 III

Wherein in formula I and III, λ represents to enter the light wavelength of retardation layer;

R represent with respect to from Z-direction, be the X-direction of incident light of normal direction and Y direction delay, be the absolute value that postpones in the face, here, X-direction be largest refractive index in the display delay layer plane direction, be slow-axis direction in the face, Y direction is direction vertical with X-direction in the retardation layer plane, is quick shaft direction in the face that Z-direction is perpendicular to the thickness direction of the retardation layer of X-direction and Y direction;

R ' expression is with respect to the incident light from the 30 ° of directions that tilt at least about Z-direction, the absolute value of the delay between X ' direction of principal axis and Y ' direction of principal axis, here, X ' direction of principal axis is in the retardation layer plane and the perpendicular axial direction of incident direction of incident light, this incident light tilts 30 ° at least about Z-direction, and Y ' direction of principal axis is and incident direction and the perpendicular direction of X ' direction of principal axis.

2. polarization member according to claim 1, wherein said retardation layer comprises the cholesteric liquid crystal compound of fixing with the planar orientation state, and the selective reflecting wavelength band of described retardation layer is present in the wavelength region may different with the visible region of 380nm to 780nm.

3. polarization member according to claim 1, wherein said retardation layer comprise the shaft-like liquid-crystal compounds of fixing with vertical orientated state.

4. polarization member according to claim 1, wherein said retardation layer comprise the disc liquid-crystal compounds of fixing with nematic phase or column phase state of orientation.

5. polarization member according to claim 1, wherein said retardation layer comprise the non-liquid crystal polymer of biaxial orienting.

6. polarization member according to claim 1, wherein said retardation layer comprises the inorganic layered compound with negative uniaxiality, the state of orientation of this inorganic layered compound is fixed to, make this retardation layer optical axis direction for perpendicular to the direction on plane, be normal direction.

7. polarization member wherein comprises two-layer reflected ray polarizer at least and places two quarter wave plate layers between the described two-layer reflected ray polarizer,

Slow axis in the face of one of described quarter wave plate layer becomes 40 ° to 50 ° angle with respect to the polarization axle of the described reflected ray polarizer layer that is positioned at the same side,

Slow axis in the face of another described quarter wave plate layer becomes-40 ° to-50 ° angle with respect to the polarization axle of the described reflected ray polarizer layer that is positioned at the same side,

The condition of formula IV below described quarter wave plate layer satisfies respectively:

Nz≥2.0 IV

Nz=(nx-nz)/(nx-ny) wherein,

Wherein, in formula IV, nx, ny and nz represent X-direction in the quarter wave plate layer respectively, the refractive index of Y direction and Z-direction, here, X-direction is that refractive index becomes maximum direction, is slow-axis direction in the face in this quarter wave plate plane, Y direction is direction vertical with X-direction in this quarter wave plate layer plane, is the interior quick shaft direction of face, and Z-direction is the thickness direction with X-direction this quarter wave plate layer vertical with Y direction.

8. polarization member wherein comprises two-layer reflected ray polarizer at least and places half-wave plate between the described two-layer reflected ray polarizer,

Slow axis becomes 40 ° to 50 ° angle with respect to the polarization axle of one of described reflected ray polarizer layer in the face of described half-wave plate, and becomes-40 ° to-50 ° angle with respect to the polarization axle of another described reflected ray polarizer layer,

The condition of formula V below described half-wave plate satisfies:

Nz≥1.5 V

Nz=(nx-nz)/(nx-ny) wherein,

In formula V, nx, ny and nz represent X-direction in the described half-wave plate respectively, the refractive index of Y direction and Z-direction, here, X-direction is that refractive index becomes maximum direction, is slow-axis direction in the face in this half-wave plate plane, and Y direction is direction vertical with X-direction this half-wave plate plane in, is the interior quick shaft direction of face, and Z-direction is the thickness direction with X-direction this half-wave plate vertical with Y direction.

9. according to each described polarization member in the claim 1,7,8, wherein the overlapping region of selective reflecting wavelength band comprises 540 to 560nm wavelength coverage in described two-layer reflected ray polarizer.

10. according to each described polarization member in the claim 1,7,8, wherein said each element comes stacked by the bonding agent of light transmission or the layer of pressure-sensitive bonding agent.

11. an image display device comprises according to each described polarization member in the claim 1,7,8.

12. a polarized light source comprises light source, reflection horizon and according to each described polarization member in the claim 1,7,8 wherein is stacked in this polarization member on the light source by this reflection horizon.

13. a LCD device comprises polarized light source according to claim 12, also is stacked with liquid crystal cell on this polarization member.