JP2006024519A - Direct backlight and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct backlight which uses a reflection polarizer, and in which light utilization efficiency is improved. <P>SOLUTION: This is the direct backlight in which in its one side, a lenticular lens array having a plurality of parallel ridges is arranged against a linear light source, in which a transmission factor incident angle depending optical element is further arranged above its one side, and in which the ridge of the lenticular lens array is arranged roughly in parallel with the major axis of the linear light source, and on the other side, has the ridge, and an reflecting plate which has a repeated slant structure is arranged so that the ridge of the reflecting plate and the major axis of the linear light source cross nearly in right angles. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a direct type backlight. The present invention also relates to a liquid crystal display device using the direct type backlight.

  A linear light source is used for the direct type backlight. A cold cathode tube used as a linear light source has a remarkably high surface luminance, and when a direct image thereof is visually recognized, non-uniformity as a surface light source is likely to occur. For this reason, in the conventional direct type backlight, a design method in which the visibility of the linear light source is reduced and the surface light source is uniform by disposing a high haze diffuser on the linear light source has been mainstream. The direct type backlight is shown in FIGS. 16 to 19, for example. In these direct type backlights, as shown in the figure, a diffusion plate 15 is disposed on a linear light source 11, and various reflectors 14-1 to 14-4 are disposed on the opposite side.

  In order to improve the luminance of the backlight, a reflective polarizer or a transmittance incident angle dependent optical element whose transmittance varies depending on the incident angle is used. As the transmittance incident angle dependent optical element, for example, an optical element using a cholesteric liquid crystal or a birefringent anisotropic multilayer laminate, a band pass filter in which the wavelength of the transmittance is controlled by vapor deposition / sputtering, or the like was used. (See Patent Documents 1 to 13, etc.). These optical elements transmit incident light in a specific direction, but incident light from other directions behaves almost like total reflection and have almost no absorption loss. For example, as shown in FIG. 20, a direct-type backlight is known in which a transmittance incident angle dependent optical element 13 is arranged.

  However, the high haze diffuser used in the direct type backlight has a tendency to deflect the light from the linear light source in an oblique direction to converge the light at an angle where it is difficult to reuse. In other words, light rays with a large incident angle with respect to the normal of the surface illuminate the inner surface of the sidewall of the backlight structure, or are confined inside the optical film at a critical angle, which increases absorption loss due to an increase in optical path length. There was a problem such as. In particular, when a transmittance incident angle dependent optical element is used for the purpose of collimating the backlight, the light reflected in the oblique direction is difficult to be reused unless it is shifted in the front direction. Further, when the transmittance incident angle dependent optical element has reflection polarization characteristics, ideally, if the reflectance of the wall surface of the backlight structure is 100%, the reflected light is emitted after the infinite number of reflections. It should be reused by shifting to the possible angle. However, in reality there is an absorption loss. Because of these problems, there was almost no attempt to optimize the direct-type backlight with a reflective polarizer.

Various types of direct-type backlights have been proposed (see Patent Documents 14 to 34, etc.), all of which improve the reflector and the high haze diffuser, and are combined with a reflective polarizer. There are few things. As the reflector, it is exemplified that a reflector having a ridge line is arranged so as to be parallel to the long axis of the linear light source (fluorescent tube) (FIG. 17).
JP 2003-337334 A JP 2003-337335 A JP 20044763 A Japanese Patent Laid-Open No. 2004-4762 US Patent Application Publication No. 2002/36735 JP-A-6-235900 Japanese Patent Laid-Open No. 2-158289 Japanese National Patent Publication No. 10-510671 US Pat. No. 6,307,604 German patent 3836955 US Patent Application Publication No. 2002/34009 International Publication No. 02/25687 Pamphlet Japanese Patent Laid-Open No. 11-212073 JP-A-11-2813 Japanese Patent Laid-Open No. 5-27237 JP-A-5-45505 JP-A-6-130384 Japanese Patent Laid-Open No. 2001-13880 JP 2002-278470 A JP 2004-22352 A JP 2004-6256 A US Pat. No. 6,692,137 US Patent Application Publication No. 2004/12971 US Patent Application Publication No. 2003/95407 US Pat. No. 6,578,990 US Patent Application Publication No. 2002/167811 US Patent Application Publication No. 2002/159261 US Pat. No. 6,494,587 US Patent Application Publication No. 2001/21110 US Pat. No. 5,975,722 US Pat. No. 5,871,273 European Patent Application No. 971258 European Patent Application Publication No. 454435 International Publication No. 02/67024 Pamphlet

  An object of the present invention is to provide a direct type backlight using a transmittance incident angle-dependent optical element and having improved light utilization efficiency.

  Another object of the present invention is to provide a liquid crystal display device using the direct type backlight.

  As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by the following direct type backlight, and have completed the present invention.

That is, the present invention relates to a linear light source.
A lenticular lens array having a plurality of parallel ridge lines is disposed on one side thereof, and a transmittance incident angle dependent optical element is disposed thereon, and the ridge line of the lenticular lens array is the long axis of the linear light source. Are arranged approximately parallel to
On the other side, a reflector having a ridge line and having a repetitive inclined structure is arranged so that the ridge line of the reflector and the long axis of the linear light source are substantially perpendicular to each other. Type backlight.

  In a conventional direct type backlight, a reflecting plate having a ridge line and having a repeated inclined structure has the ridge line arranged in parallel to the long axis of the linear light source. Such an arrangement of the reflecting plates is highly efficient in the case of directly reflecting the light emitted from the linear light source. Moreover, there was an effect of making it difficult to visually recognize the direct image of the linear light source. However, when a transmittance incident angle dependent optical element is used in such a reflector arrangement, the reuse efficiency of the return beam from the transmittance incident angle dependent optical element is low. In addition, the high haze diffuser plate used in the conventional direct type backlight is omnidirectionally diffused, and the amount of light rays in the oblique direction increases. Therefore, the shift to an angle that cannot be used for display is large.

  In the direct type backlight of the present invention, contrary to the conventional direct type backlight, the reflector arranged immediately below the linear light source is arranged so that its ridgeline and the long axis of the linear light source are substantially orthogonal to each other. Yes. On the linear light source, the lenticular lens array is arranged so that its ridge line is substantially parallel to the long axis of the linear light source. With this configuration, the light beam in the short axis direction of the linear light source is diffused and uniformed by the effect of the anisotropic diffusion plate of the lenticular lens array. Therefore, the direct image of the linear light source is not visually recognized in combination with the adjacent image, and can be visually recognized as a uniform planar light source. On the other hand, the light beam in the major axis direction does not undergo angular change. For this reason, it is possible to reduce the probability that the return ray of the transmittance incident angle dependent optical element shifts to an angle that cannot be reused, and to improve the light utilization efficiency.

  In the direct type backlight, the lenticular lens array and the transmittance incident angle dependent optical element are arranged in the order of the linear light source, the lenticular lens array, and the transmittance incident angle dependent optical element.

  It is desired that the optical element disposed closer to the liquid crystal panel (viewing side) than the transmittance incident angle dependent optical element has a sufficiently small phase difference and low depolarization ability. Therefore, it is preferable that the lenticular lens array and the reflective polarizer are arranged in the order of the linear light source, the lenticular lens array, and the transmittance incident angle dependent optical element. When arranged in this order, the in-plane phase difference of the lenticular lens array need not be considered.

  In the direct type backlight, a diffusion plate can be further arranged on the side where the lenticular lens array and the transmittance incident angle dependent optical element are arranged with respect to the linear light source.

  The arrangement of the diffusing plate can prevent the structure of the lenticular lens array and the repeated inclined structure of the reflecting plate from being visually recognized. In order to eliminate the visibility of the structure of the lenticular lens array, the diffuser plate is disposed on the viewing side with respect to the lenticular lens array. In order to eliminate the visibility of the repeated inclined structure of the reflecting plate, the diffusing plate is arranged closer to the linear light source than the lenticular lens array.

  As described above, it is desirable that the optical element arranged on the liquid crystal panel side (viewing side) from the transmittance incident angle dependent optical element has a sufficiently small phase difference and low depolarization ability. Therefore, when the diffuser plate is arranged closer to the linear light source than the transmittance incident angle dependent optical element, the in-plane retardation of the diffuser plate need not be considered. On the other hand, when the diffuser plate is arranged on the viewer side with respect to the transmittance incident angle dependent optical element, the in-plane retardation of the diffuser plate is preferably 30 nm or less, and more preferably 20 nm or less.

  In the direct type backlight, the inclination angle of the inclined structure of the reflector is preferably 5 to 40 degrees.

  As shown in the conceptual diagram of FIG. 13, when the inclination angle θ of the inclined structure of the reflecting plate is 45 degrees or more, it becomes a light trap, and the light beam r from the linear light source is absorbed. As shown in the conceptual diagram of FIG. 14, when the inclination angle θ is around 45 degrees, the reflecting plate functions as a retroreflecting plate, and the light rays are returned to the linear light source and absorbed. In consideration of such matters, the inclination angle θ of the inclined structure of the reflector is preferably 5 to 40 degrees. As shown in the conceptual diagram in FIG. 15, the inclination angle in the above range has a function of returning light having a large incident angle to the front direction, and the light reuse efficiency of the reflective polarizer can be further increased. The inclination angle θ is more preferably 10 to 35 degrees.

  In the direct type backlight, as the transmittance incident angle dependent optical element, a band-pass filter that transmits the bright line spectrum of the light source at a specific incident angle and reflects it at other angles can be used.

  Examples of the band pass filter include stretched bodies of multilayer laminates of resin materials having different refractive indexes. Examples of the bandpass filter include vapor-deposited multilayer thin films of inorganic oxides having different refractive indexes.

  Examples of the bandpass filter include a laminate of cholesteric liquid crystal layers. As the laminate of cholesteric liquid crystal layers, those having a central wavelength of selective reflection of three or more and each selective reflection wavelength band not overlapping are preferably used.

  In the direct type backlight, a laminate of two or more reflective polarizers can be used as the transmittance incident angle dependent optical element. As the laminate of reflective polarizers, a laminate of broadband cholesteric liquid crystal layers in which two or more selective reflection wavelength bands overlap each other can be used. As the transmittance incident angle dependent optical element, one having one or more kinds of retardation plates between the layers of the reflective polarizer laminate can be used.

  The present invention also relates to a liquid crystal display device using the direct type backlight.

  The direct type backlight of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, in the direct type backlight of the present invention, a lenticular lens array 2 and a transmittance incident angle dependent optical element 3 are arranged on one side of a linear light source 1. The lenticular lens array 2 has a plurality of parallel ridge lines a, and the ridge lines a are arranged substantially parallel to the long axis b of the linear light source 1. In FIG. 1, a linear light source 1, a lenticular lens array 2, and a transmittance incident angle dependent optical element 3 are arranged in this order. The fact that the ridge line a and the major axis b are substantially parallel means that a small angle between them is preferably 20 degrees or less, and further 10 degrees or less.

  On the other side of the linear light source 1, a reflecting plate 4 is disposed. The reflector 4 has a ridge line c and has a repeated inclined structure. The ridgeline c of the reflecting plate 4 and the long axis b of the linear light source 1 are arranged so as to be substantially orthogonal. The fact that the ridge line c and the major axis b are substantially orthogonal means that the angle formed by both is preferably 90 ° ± 20 °, more preferably 90 ° ± 10 °.

  2 to 4 show examples in which the diffusion plate 5 is disposed in the direct type backlight of the present invention. In FIG. 2, in the direct type backlight of FIG. 1, the diffusing plate 5 is arranged on the viewing side from the transmittance incident angle dependent optical element 3.

  In FIG. 3, a diffusion plate 5 is disposed between the lenticular lens array 2 and the transmittance incident angle dependent optical element 3. In FIG. 4, a diffusion plate 5 is arranged between the linear light source 1 and the lenticular lens array 2. In the case of FIGS. 3 and 4, the phase difference of the lenticular lens array 2 and the diffusion plate 5 need not be considered.

  In FIGS. 1 to 4, the lenticular lens array 2 is arranged with the surface structure having the ridge line a facing upward (toward the viewing side), but the arrangement direction of the surface structure is not particularly limited, and the lenticular lens array 2 is arranged. The arrangement direction can be determined in a timely manner according to the design. The direct type backlight of FIG. 5 is an example when the arrangement direction of the surface structure of the lenticular lens array 2 is downward (toward the light source side). FIG. 5 has the same configuration as FIG. 4 except for the arrangement direction of the surface structure of the lenticular lens array 2. The lenticular lens array 2 may be one having a surface structure having a ridge line a on both sides. The direct type backlight of FIG. 6 is an example in which the lenticular lens array 2 having the surface structure on both sides is used. 6 has the same configuration as that of FIG. 4 except that the lenticular lens array 2 having the surface structure on both sides is used.

  Hereinafter, each configuration of the direct type backlight of the present invention will be described.

(Linear light source)
As the linear light source, those used in direct type backlights can be used without particular limitation. For example, a cold cathode tube is used.

(Lenticular lens array)
A lenticular lens array having a plurality of parallel ridge lines and capable of functioning as an anisotropic diffusion plate can be used without particular limitation. The focal length and the lens pitch of the lens in the lenticular lens array are not particularly limited, but in order to prevent the direct image of the linear light source from being visually recognized, the lens focal length is determined by the lenticular lens array, the linear light source, and the like. It is preferable that the distance between the two is shorter. Further, in order to smooth and uniform the in-plane luminance so that the lens pitch is not visually recognized, the lens pitch is preferably 1 mm or less, and more preferably 0.5 mm or less. Moreover, it is preferable that the numerical aperture of each lens is large. Numerical aperture = n · sin θ (n: refractive index of lens, θ: expected angle formed by focal length of lens and lens periphery). This is because it is preferable that the taking-in angle into the lens is large for enlarging the linear light source images arranged at intervals. When it is difficult to obtain a sufficient numerical aperture, a Fresnel lens type obtained by dividing a lenticular lens may be used in combination. If a Fresnel lens is used, the thickness can be reduced.

  The lenticular lens array generally has a structure in which a large number of kamaboko-like structures as shown in FIG. 7 are arranged in parallel. FIG. 9 shows a cross-sectional view thereof. In order to prevent moiré with the liquid crystal panel, a random undulation structure as shown in FIG. 8 may be provided. In order to prevent moiré, the ridgeline may have a slight angle with respect to the side direction of the liquid crystal panel.

  Although the lenticular lens array has the effect of bending incident light in only one direction due to surface refraction, it is preferable that the diffusion angle is large in order to diffuse a linear light source and spread it into a planar shape as in the present invention. For this reason, the lens curve may become tight and the lens thickness may increase. In order to reduce the thickness, it is effective to use a Fresnel lens. FIG. 10 shows a cross-sectional view of a lenticular lens array formed into a Fresnel lens. 9 and 10 are lenses having the same curve, but the Fresnel lens divided as shown in FIG. 10 can easily reduce the thickness to 1/3 or less compared to FIG.

  The production method of the lenticular lens array is not particularly limited, and various methods can be adopted. For example, a method of obtaining a shape transfer of a thermoplastic resin such as polycarbonate, polymethyl methacrylate, norbornene resin from a mold; using a UV curable resin on the surface of a transparent substrate such as polyethylene terephthalate or triacetyl cellulose. Method obtained by shape transfer; Method obtained by mask exposure using UV curable resin; Method obtained by etching treatment; Method of transferring mold shape using thermosetting resin such as epoxy resin; Stress applied to resin film And a method using a crazed structure having a surface shape and a wavy structure of the surface shape; a method in which transparent fibers and transparent round bars are arranged in parallel and fixed.

  As described above, the manufacturing method and material of the lenticular lens array are not particularly limited, but it is preferable that the total light transmittance of the lenticular lens array is high from the viewpoint of effective use of light. The total light transmittance is preferably 80% or more, more preferably 90% or more.

(Transmission incident angle dependent optical element)
As the transmittance incident angle-dependent optical element, for example, those described in Patent Documents 1 to 12 can be used.

  Examples of the transmittance incident angle-dependent optical element include a band-pass filter that transmits the bright line spectrum of the light source at a specific incident angle and reflects it at other angles. For example, one that transmits normal incident light and reflects oblique incident light. The bandpass filter is preferably combined with a light source having an emission line spectrum. That is, a band-pass filter that transmits the bright line spectrum of the light source at a specific incident angle and reflects it at other angles is preferable. Specifically, the band-pass filter can be a stretched product of a multilayer laminate of resin materials having different refractive indexes, and an inorganic oxide vapor-deposited thin film having different refractive indexes.

  Also, the transmittance incident angle dependent optical element transmits a polarized light component in one direction of a normal incident light beam and selectively reflects the other polarized light component, and reflects an oblique incident light beam regardless of the direction of the polarized light. can give. Such an incident angle-dependent optical element transmits a circularly polarized light and selectively reflects the opposite circularly polarized light, and transmits one of the orthogonal linearly polarized light and the other. There is a type that reflects automatically. Examples of the circularly polarized light incident angle-dependent optical element include those using at least one cholesteric liquid crystal polymer layer. The cholesteric liquid crystal polymer layer can be a laminate of cholesteric liquid crystals in which two or more layers are laminated. The bandpass filter is preferably combined with a light source having an emission line spectrum. The laminate of cholesteric liquid crystal layers preferably has three or more central wavelengths of selective reflection, and the selective reflection wavelength bands do not overlap each other. On the other hand, as the linearly polarized light incident angle-dependent optical element, a multilayered laminate of birefringent anisotropic bodies can be used.

  As the transmittance incident angle dependent optical element, a laminate of two or more reflective polarizers can be used.

  For example, as a transmittance incident angle dependent optical element using a laminate of two or more layers of reflective polarizers, at least two layers of reflective polarizers (a) in which the wavelength bands of selective reflection of polarized light overlap each other are used. The optical element (Z) in which the retardation layer (b) is disposed therebetween can be used. Regarding the optical element (Z), there are a circularly polarized light type and a linearly polarized light type. Hereinafter, the optical element (Z) will be exemplified and described.

(Example 1)
The reflective polarizer (a) is a circularly polarized reflective polarizer (a1) that transmits certain circularly polarized light and selectively reflects reverse circularly polarized light,
The retardation layer (b) has a front retardation (normal direction) of substantially zero and a retardation layer (b1) of λ / 8 or more with respect to incident light incident with an inclination of 30 ° or more with respect to the normal direction. An optical element having.

(Example 2)
The reflective polarizer (a) is a linearly polarized reflective polarizer (a2) that transmits one of orthogonal linearly polarized light and selectively reflects the other, and
The retardation layer (b) has a retardation layer (b1) having a front phase difference (normal direction) of substantially zero and λ / 4 or more with respect to incident light incident with an inclination of 30 ° or more with respect to the normal direction. Have
On both sides of the retardation layer (b1), there is a layer (b2) having a front phase difference of approximately λ / 4 between the linearly polarized reflective polarizer (a2) and
The incident-side layer (b2) is at an angle of 45 ° (−45 °) ± 5 ° with respect to the polarization axis of the incident-side linearly polarized reflective polarizer (a2).
The exit side layer (b2) is at an angle of −45 ° (+ 45 °) ± 5 ° with respect to the polarization axis of the output side linearly polarized reflective polarizer (a2).
The incident-side layer (b2) and the emission-side layer (b2) are arranged so that the angle formed by the mutual slow axes is an arbitrary angle.

(Example 3)
The reflective polarizer (a) is a linearly polarized reflective polarizer (a2) that transmits one of orthogonal linearly polarized light and selectively reflects the other, and
The retardation layer (b) has two biaxial retardation layers (b3) having a front retardation of approximately λ / 4 and an Nz coefficient of 2 or more,
In the incident side layer (b3), the slow layer axis direction is at an angle of 45 ° (−45 °) ± 5 ° with respect to the polarization axis of the linearly polarized reflective polarizer (a2) on the incident side.
The outgoing layer (b3) has a slow layer axis direction of −45 ° (+ 45 °) ± 5 ° with respect to the polarization axis of the linearly polarized reflective polarizer (a2) on the outgoing side,
The incident-side layer (b3) and the emission-side layer (b3) are optical elements that are arranged so that their slow axes are at an arbitrary angle.

(Example 4)
The reflective polarizer (a) is a linearly polarized reflective polarizer (a2) that transmits one of orthogonal linearly polarized light and selectively reflects the other, and
The retardation layer (b) has one biaxial retardation layer (b4) having a front retardation of approximately λ / 2 and an Nz coefficient of 1.5 or more,
The slow axis direction of the incident side layer is at an angle of 45 ° (−45 °) ± 5 ° with respect to the polarization axis of the linearly polarized reflective polarizer (a2) on the incident side,
The slow axis direction of the outgoing layer is at an angle of −45 ° (+ 45 °) ± 5 ° with respect to the polarization axis of the linearly polarized reflective polarizer (a2) on the outgoing side,
The polarization axes of the two linearly polarized reflective polarizers (a2) are substantially orthogonal,
Placed optical element.

(Example 5)
At least one layer of reflective polarizer (a) is a circularly polarized reflective polarizer (a1) that transmits certain circularly polarized light and selectively reflects opposite circularly polarized light,
The at least one layer of reflective polarizer (a) is a linearly polarized reflective polarizer (a2) that transmits one of orthogonal linearly polarized light and selectively reflects the other,
The retardation layer (b) has a front phase difference (normal direction) of approximately λ / 4 and a phase difference value of λ / 8 or more with respect to incident light incident with an inclination of 30 ° or more with respect to the normal direction. An optical element which is a layer (b1) having

(Reflective polarizer (a))
It is desirable that total reflection is achieved with respect to light having a wavelength near 550 nm, which has high visibility from the viewpoint of improving luminance, and the selective reflection wavelength of the reflective polarizer (a) is at least in the wavelength region of 550 nm ± 10 nm. It is desirable that they overlap. Further, it is more desirable that the reflection wavelength bands overlap in the visible light all-wavelength region 380 nm to 780 nm from the viewpoint of coloring and the viewpoint of RGB corresponding to a liquid crystal display device or the like.

(Circularly polarized reflective polarizer (a1))
As the circularly polarized reflective polarizer (a1), for example, a cholesteric liquid crystal material is used. In the circularly polarized reflective polarizer (a1), the center wavelength of selective reflection is determined by λ = np (n is the refractive index of the cholesteric material, and p is the chiral pitch). For obliquely incident light, the selective reflection wavelength is blue-shifted, so that the overlapping wavelength region is preferably wider.

  In the case where the circularly polarized reflective polarizer (a1) is a cholesteric material, if the phase difference is zero or λ when the front phase difference is tilted by λ / 2 with the same concept even in a combination of different types (right twist and left twist) A similar polarizer can be obtained, but this is not preferable because problems such as anisotropy and coloring due to the azimuth angle of the inclined axis occur. From this point of view, combinations of the same type (right-twisted, left-twisted) are preferable, but coloring can be suppressed by canceling with a combination of upper and lower cholesteric liquid crystal molecules or C-plates having different wavelength dispersion characteristics. .

  Any suitable cholesteric liquid crystal may be used for the circularly polarizing reflective polarizer (a1), and there is no particular limitation. For example, a liquid crystal polymer exhibiting cholesteric liquid crystallinity at high temperature, a polymerizable liquid crystal obtained by polymerizing a liquid crystal monomer and, if necessary, a chiral agent and an alignment aid by irradiation with ionizing radiation such as an electron beam or ultraviolet rays or heat, A mixture etc. are mention | raise | lifted. The liquid crystallinity may be either lyotropic or thermotropic, but is preferably a thermotropic liquid crystal from the viewpoint of ease of control and ease of formation of a monodomain.

  The cholesteric liquid crystal layer can be formed by a method according to a conventional alignment process. For example, rayon is formed by forming a film of polyimide, polyvinyl alcohol, polyester, polyarylate, polyamide imide, polyether imide, etc. on a support substrate having a birefringence retardation as small as possible such as triacetyl cellulose or amorphous polyolefin. An alignment film rubbed with a cloth or the like, an obliquely deposited layer of SiO, or a substrate using the surface properties of a stretched substrate such as polyethylene terephthalate or polyethylene naphthalate as an alignment film, or the above substrate surface is rubbed or bentara A substrate that has been processed with a fine polishing agent represented by the above and formed fine irregularities having fine alignment regulating force on the surface, or an alignment film that generates liquid crystal regulating force by light irradiation such as an azobenzene compound on the substrate film A liquid crystal polymer is applied on a suitable alignment film composed of a base material formed with Open and heat to above the glass transition temperature and below the isotropic phase transition temperature, and in a state where the liquid crystal polymer molecules are in a planar orientation, cool to below the glass transition temperature to form a solidified layer in which the orientation is fixed And how to do it.

  Further, the structure may be fixed by irradiation of energy such as ultraviolet rays or ion beams at the stage where the alignment state is formed. The base material having a small birefringence may be used as it is as a liquid crystal layer support. In the case where the birefringence is large or the demand for the thickness of the optical element is severe, the liquid crystal layer can be peeled off from the alignment substrate and used appropriately.

  The liquid crystal polymer film is formed by, for example, thinning a solution of a liquid crystal polymer in a solvent by spin coating, roll coating, flow coating, printing, dip coating, casting film formation, bar coating, or gravure printing. It can be carried out by a method of developing a layer and drying it as necessary. Examples of the solvent include chlorinated solvents such as methylene chloride, trichloroethylene, and tetrachloroethane; ketone-based solvents such as acetone, methyl ethyl ketone, and cyclohexanone; aromatic solvents such as toluene; cyclic alkanes such as cycloheptane; or N -Methyl pyrrolidone, tetrahydrofuran, etc. can be used suitably.

  In addition, a heating melt of a liquid crystal polymer, preferably a heating melt exhibiting an isotropic phase, is developed according to the above, and a thin layer is further developed and solidified while maintaining the melting temperature as necessary. can do. This method is a method that does not use a solvent. Therefore, the liquid crystal polymer can be developed even by a method that provides good hygiene in the working environment. In developing the liquid crystal polymer, a superposition method of a cholesteric liquid crystal layer through an alignment film can be adopted as necessary for the purpose of thinning.

  Furthermore, if necessary, these optical layers can be peeled off from the supporting substrate / orienting substrate used at the time of film formation and transferred to other optical materials for use.

  In addition, as the circularly polarized reflective polarizer (a1) of the present invention, a combination of a later-described linearly polarized reflective polarizer (a2) and a λ / 4 plate can be used. One of these may be used, or two or more may be used. The circularly polarized reflective polarizer (a1) may be a combination of a linearly polarized reflective polarizer and a λ / 4 plate. When used for the lowermost layer (for example, the first sheet from the backlight side), the linearly polarized reflective polarizer and then the λ / 4 plate are arranged in this order from the backlight side. When used for the uppermost layer, the λ / 4 plate and then the linearly polarized reflective polarizer are arranged in this order from the backlight side. When used for an intermediate layer (for example, the second one from the backlight side when three layers are stacked), λ / 4 plates are arranged on both sides of the linearly polarized reflective polarizer.

(Linear polarization type reflective polarizer (a2))
As the linearly polarized reflective polarizer (a2), a grid-type polarizer, a multilayer thin film laminate of two or more layers made of two or more materials having a difference in refractive index, and a vapor deposited multilayer thin film having different refractive indexes used for a beam splitter, etc. , Two or more birefringent layer multilayer thin film laminates made of two or more materials having birefringence, two or more resin laminates using two or more resins having birefringence, stretched linearly polarized light For example, it may be separated by reflecting / transmitting in an orthogonal axial direction.

  For example, phase difference expression such as polyethylene naphthalate, polyethylene terephthalate, materials that generate phase difference by stretching such as polycarbonate, acrylic resin typified by polymethyl methacrylate, norbornene resin typified by JSR Arton, etc. A resin obtained by uniaxially stretching a small amount of resin alternately as a multilayer laminate can be used.

(Phase difference layer (b))
The retardation layer (b1) disposed between the circularly polarized reflective polarizer (a1) or the linearly polarized reflective polarizer (a2) has a substantially zero phase difference in the front direction and is 30 ° from the normal direction. It has a phase difference of λ / 8 or more with respect to incident light at an angle. Since the front phase difference is intended to maintain vertically incident polarized light, it is desirable that the front phase difference be λ / 10 or less.

  For incident light from an oblique direction, it is determined as appropriate depending on the angle at which it is totally reflected so as to be efficiently polarized and converted. For example, in order to achieve total reflection at an angle of about 60 ° from the normal line, the phase difference when measured at 60 ° may be determined to be about λ / 2. However, the transmitted light from the circularly polarized reflective polarizer (a1) changes its polarization state due to the C-plate-like birefringence of the circularly polarized reflective polarizer (a1) itself. The phase difference measured at that angle of the plate may be a value smaller than λ / 2. Since the phase difference of the C plate increases monotonously as the incident light is tilted, λ / 8 or more with respect to incident light at an angle of 30 ° as a guide for causing effective total reflection when tilted at an angle of 30 ° or more. Just have it.

  In the case where the optical element (Z) according to the present invention is designed so as to effectively shield light rays having an incident angle of 30 ° from the front, the transmitted light beam is sufficiently transmitted in a region where the incident angle is approximately 20 °. It is falling. When limited to the light rays in this region, only the light rays in the region showing good display of a general TN liquid crystal display device are transmitted. It is used for enlarging the viewing angle in the present invention because it varies depending on conditions such as the type of liquid crystal in the cell, orientation state, pretilt angle, etc. of the TN liquid crystal display device used, but gradation inversion and rapid contrast deterioration do not occur. It becomes a standard. In order to narrow down to only the front light, the phase difference value of the phase difference layer may be set larger, or the phase difference value may be reduced and the narrowing down may be performed on the premise that the compensation phase difference plate is combined with the TN liquid crystal. .

  The material of the retardation layer (b1) is not particularly limited as long as it has the above optical characteristics. For example, a planar alignment state of a cholesteric liquid crystal having a selective reflection wavelength other than a visible light region (380 nm to 780 nm), a homeotropic alignment state of a rod-like liquid crystal, a columnar alignment or a nematic alignment of a discotic liquid crystal , A negative uniaxial crystal oriented in the plane, a biaxially oriented polymer film, and the like.

  As the C plate, for example, the C plate in which the planar alignment state of the cholesteric liquid crystal having a selective reflection wavelength other than the visible light region (380 nm to 780 nm) is fixed, the selective reflection wavelength of the cholesteric liquid crystal is colored in the visible light region, etc. It is desirable that there is no. Therefore, it is necessary that the selectively reflected light is not in the visible region. The selective reflection is uniquely determined by the cholesteric chiral pitch and the refractive index of the liquid crystal. Although the value of the center wavelength of selective reflection may be in the near-infrared region, it is more desirable to be in the ultraviolet region of 350 nm or less because it is affected by the optical rotation and a slightly complicated phenomenon occurs. The formation of the cholesteric liquid crystal layer is performed in the same manner as the formation of the cholesteric layer in the above-described reflective polarizer.

  The C plate with a fixed homeotropic alignment state is obtained by polymerizing a liquid crystalline thermoplastic resin or liquid crystal monomer exhibiting nematic liquid crystal properties at high temperature and, if necessary, an alignment aid by irradiation with ionizing radiation such as electron beams or ultraviolet rays or heat. A polymerizable liquid crystal or a mixture thereof is used. The liquid crystallinity may be either lyotropic or thermotropic, but is preferably a thermotropic liquid crystal from the viewpoint of ease of control and ease of formation of a monodomain. Homeotropic alignment is obtained, for example, by coating the birefringent material on a film on which a vertical alignment film (long-chain alkylsilane or the like) is formed, and expressing and fixing a liquid crystal state.

  As a C plate using a discotic liquid crystal, a discotic liquid crystal material having a negative uniaxial property such as a phthalocyanine or a triphenylene compound having an in-plane molecular spread as a liquid crystal material, a nematic phase or a columnar phase is used. It is expressed and fixed. Examples of the negative uniaxial inorganic layered compound are detailed in JP-A-6-82777.

  C plate using biaxial orientation of polymer film is a method of biaxially stretching a polymer film having positive refractive index anisotropy in a balanced manner, a method of pressing a thermoplastic resin, and cutting out from a parallel oriented crystal. It is obtained by a method.

  When the linearly polarized reflective polarizer (a2) is used, as the retardation layer (b1), the phase difference in the front direction is substantially zero, and the incident light at an angle of 30 ° from the normal direction is λ / Those having a phase difference of 4 or more are used. A method similar to that of the above-described circularly polarizing plate after linearly polarized light is once converted into circularly polarized light using a λ / 4 plate (b2) having a front phase difference of approximately λ / 4 on both sides of the retardation layer (b1). Can be collimated. In this case, the angle formed between the slow axis of the λ / 4 plate (b2) and the polarization axis of the linearly polarized reflective polarizer (a2) is as described above, and the axial angle between the λ / 4 plates (b2) is arbitrary. Can be set.

  Specifically, a λ / 4 plate is used as the retardation layer (b2). As the λ / 4 plate, an appropriate retardation plate is used according to the purpose of use. The λ / 4 plate can control two or more kinds of retardation plates to control optical characteristics such as retardation. As the retardation plate, a birefringent film formed by stretching a film made of an appropriate polymer such as polycarbonate, norbornene resin, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefins, polyarylate, polyamide, Examples thereof include an alignment film made of a liquid crystal material such as a liquid crystal polymer, and an alignment layer of the liquid crystal material supported by the film.

  A retardation plate that functions as a λ / 4 plate in a wide wavelength range such as a visible light region is, for example, a retardation layer that functions as a λ / 4 plate for light-colored light having a wavelength of 550 nm and a retardation that exhibits other retardation characteristics. It can be obtained by a method of superimposing a layer, for example, a retardation layer functioning as a half-wave plate. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

  Further, the same effect can be obtained by arranging two biaxial retardation layers (b3) having a front phase difference of approximately λ / 4 and a thickness direction retardation of λ / 2 or more. . The biaxial retardation layer (b3) satisfies the above requirements if the Nz coefficient is approximately 2 or more. In this case, the slow axis with respect to the biaxial retardation layer (b3) and the polarization axis of the linearly polarized reflective polarizer (a2) are as described above, and the axial angle between the biaxial retardation layers (b3). Can be set arbitrarily.

  The front phase difference of about λ / 4 is preferably within the range of about λ / 4 ± 40 nm, more preferably ± 15 nm, for light having a wavelength of 550 nm.

  The same effect can also be obtained by using one biaxial retardation layer (b4) having a front phase difference of approximately λ / 2 and a thickness direction retardation of λ / 2 or more. The biaxial retardation layer (b4) satisfies the above requirements if the Nz coefficient is approximately 1.5 or more. In this case, the relationship between the axial angles of the upper and lower linearly polarizing reflective polarizers (a2) and the central biaxial retardation layer (b4) is an angle as specified and is uniquely determined.

  The front phase difference of approximately λ / 2 is preferably within the range of λ / 2 ± 40 nm, more preferably ± 15 nm, for light having a wavelength of 550 nm.

  Specifically, as the biaxial retardation layers (b3) and (b4), a biaxially stretched plastic material such as polycarbonate or polyethylene terephthalate, or a liquid crystal material is uniaxially oriented in the plane direction. A hybrid-oriented material further oriented in the thickness direction is used. A liquid crystal material in which the liquid crystal material is uniaxially homeotropically aligned is also possible, and is performed in the same manner as the method of forming the cholesteric liquid crystal. However, it is necessary to use a nematic liquid crystal material instead of a cholesteric liquid crystal.

  In addition, as a transmittance incident angle dependent optical element using a laminate of two or more layers of reflective polarizers, a broadband cholesteric liquid crystal layer having a reflection bandwidth of 200 nm or more, in which two or more selective reflection wavelength bands overlap each other. A laminate using a polarizing element (A), a polarizing element (B), or the like that satisfies certain characteristics such as the following distortion rate can be used. The distortion rate is as follows.

  (Distortion rate): In order to evaluate the distortion rate of the polarizing element, the transmission spectrum of the sample was measured with an instantaneous multiphotometer (MCPD-2000 manufactured by Otsuka Electronics Co., Ltd.). When natural light is projected and the sample is installed perpendicularly to the projected light (measurement of outgoing light from the front), and when the sample is installed at an angle of 60 ° from the vertical direction (measurement of 60 ° outgoing light) About each, the state of the light which permeate | transmitted them was measured with the polarizing plate arrange | positioned at the output side, and the transmission spectrum when a polarizing plate was rotated 10 degree | times was measured. As the polarizing plate, a Sigma-Optical Gram Thompson prism polarizer was used (extinction ratio of 0.00001 or less). The distortion rate was obtained from the following calculation formula. Strain rate = minimum transmittance / maximum transmittance.

(Example 11)
A polarizing element (A) formed of cholesteric liquid crystal that emits polarized light by separating the polarized light, and a polarizing element (A ′) formed of cholesteric liquid crystal having a spiral direction opposite to that of the polarizing element (A) Are arranged with a half-wave plate (B) in between,
The polarizing element (A) and the polarizing element (A ′) are
The outgoing light with respect to the incident light in the normal direction has a distortion rate of 0.5 or more,
The outgoing light with respect to the incident light that is inclined by 60 ° or more from the normal direction has a distortion rate of 0.2 or less,
An optical element (Japanese Patent Application No. 2003-363186) characterized in that the linearly polarized light component of outgoing light increases as the incident angle increases.

(Example 12)
A polarizing element (A) formed of cholesteric liquid crystal that emits polarized light by separating the polarized light, and a polarizing element (A ′) formed of cholesteric liquid crystal having a spiral direction opposite to that of the polarizing element (A) Are arranged with a half-wave plate (B) in between, and further, a polarizing element (A) is arranged on the side of the polarizing element (A ′) with a half-wave plate (B) in between. An optical element,
The polarizing element (A) and the polarizing element (A ′) are
The outgoing light with respect to the incident light in the normal direction has a distortion rate of 0.5 or more,
The outgoing light with respect to the incident light that is inclined by 60 ° or more from the normal direction has a distortion rate of 0.2 or less,
An optical element (Japanese Patent Application No. 2003-363166) characterized in that the linearly polarized component of outgoing light increases as the incident angle increases.

  In the polarizing elements (A) and (A ′) of Examples 11 and 12, the linearly polarized component of the emitted light that increases as the incident angle increases is linear in a direction substantially orthogonal to the normal direction of the polarizing element surface. The linearly polarized light component of the emitted light that increases as the incident angle increases can be linearly polarized in a direction substantially parallel to the normal direction of the polarizing element surface. It may have a polarization axis (A2).

(Example 13)
A polarizing element (A1) formed of cholesteric liquid crystal that emits polarized light by separating incident light and a polarizing element (A2) formed of cholesteric liquid crystal having the same spiral direction as the polarizing element (A1) are arranged. An optical element,
The polarizing element (A1) and the polarizing element (A2) are both
The outgoing light with respect to the incident light in the normal direction has a distortion rate of 0.5 or more,
The outgoing light with respect to the incident light that is inclined by 60 ° or more from the normal direction has a distortion rate of 0.2 or less,
The linearly polarized light component of the emitted light increases as the incident angle increases, and
In the polarizing element (A1), the linearly polarized light component of the emitted light that increases as the incident angle increases has a polarization axis of linearly polarized light in a direction substantially orthogonal to the normal direction of the polarizing element surface.
In the polarizing element (A2), the linearly polarized light component of the emitted light that increases as the incident angle increases has a polarization axis of linearly polarized light in a direction substantially parallel to the normal direction of the polarizing element surface. An optical element (Japanese Patent Application No. 2004-78753).

(Example 14)
A polarizing element (A1) formed of cholesteric liquid crystal that emits polarized light by separating incident light and a polarizing element (A2) formed of cholesteric liquid crystal having the same spiral direction as the polarizing element (A1) are arranged. An optical element (X),
The polarizing element (A1) and the polarizing element (A2) are both
The outgoing light with respect to the incident light in the normal direction has a distortion rate of 0.5 or more,
The outgoing light with respect to the incident light that is inclined by 60 ° or more from the normal direction has a distortion rate of 0.2 or less,
The linearly polarized light component of the emitted light increases as the incident angle increases, and
In the polarizing element (A1), the linearly polarized light component of the emitted light that increases as the incident angle increases has a polarization axis of linearly polarized light in a direction substantially orthogonal to the normal direction of the polarizing element surface.
The polarizing element (A2) is an optical element in which the linearly polarized light component of the emitted light that increases as the incident angle increases has a polarization axis of linearly polarized light in a direction substantially parallel to the normal direction of the polarizing element surface. (X)
Further, an optical element (Japanese Patent Application No. 2004-78764), wherein a circularly polarized reflective polarizer (C) is disposed on either side of the polarizing element (A1) or the polarizing element (A2).

  As described above, the polarizing elements (A) and (A ′) of the present invention can be formed of a cholesteric liquid crystal layer having a reflection bandwidth of 200 nm or more. The cholesteric liquid crystal layer can be formed by stacking cholesteric liquid crystal layers having a plurality of different selective reflection wavelength bands. Further, a cholesteric liquid crystal layer whose pitch length continuously changes in the thickness direction can be used.

  The difference in the axial direction of linearly polarized light of obliquely transmitted light such as the polarizing element (A) and the polarizing element (A ′) can be arbitrarily produced depending on the stacking order of the cholesteric liquid crystal layers and the production method. In the case of a polarization splitting element with a general Brewster angle, the transmitted light in the oblique direction is uniquely defined, and only those having a linearly polarized light axis in a direction substantially parallel to the normal of the optical surface can be obtained. Absent.

  The selective reflection wavelength band of the polarizing element (A) and the polarizing element (A ′) includes at least 550 nm, preferably 100 nm or more, more preferably 200 nm or more, and further preferably 300 nm or more. Note that the polarizing element (A) and the polarizing element (A ′) can be the same in the direction of circularly polarized light transmitted in the front direction and the same selective reflection wavelength band, but the selective reflection wavelength band is It is not limited.

(Laminated body of cholesteric liquid crystal layer)
In the case where the polarizing element is a laminate of cholesteric liquid crystal layers having a plurality of different selective reflection wavelength bands, each cholesteric liquid crystal layer appropriately includes a plurality of cholesteric liquid crystal layers so that the reflection bandwidth of the laminate is 200 nm or more. Select and stack.

  A suitable cholesteric liquid crystal layer may be used without any particular limitation. The cholesteric liquid crystal layer may be the same as the cholesteric liquid crystal constituting the circularly polarized reflective polarizer (a1).

  Cholesteric liquid crystal layer stacking methods include the method of laminating a plurality of individually produced cholesteric liquid crystal layers with an adhesive or adhesive, the method of crimping after swelling or dissolving the surface with a solvent, etc., heat, ultrasonic waves, etc. The crimping method is given while adding. Moreover, after producing a cholesteric liquid crystal layer, methods, such as overlaying the cholesteric liquid crystal layer which has another selective reflection center wavelength on this layer, can be used.

(Production method of cholesteric liquid crystal layer covering visible light wavelength range)
Examples of a method for producing a cholesteric liquid crystal layer covering the visible light wavelength range include a method of irradiating the composition with an ionizing radiation such as an electron beam or an ultraviolet ray by the following method using a composition containing the same liquid crystal monomer as described above. . For example, a method using a difference in polymerization rate due to a difference in ultraviolet transmittance in the thickness direction (Japanese Patent Laid-Open No. 2000-95883), a method of extracting with a solvent and forming a concentration difference in the thickness direction (Japanese Patent No. 3062150) And a method of performing the second polymerization by changing the temperature after the first polymerization (US Pat. No. 6,057,008) and the like.

  In addition, a step of applying a liquid crystal mixture containing a polymerizable mesogenic compound (a) and a polymerizable chiral agent (b) to an alignment substrate, and a state in which the liquid crystal mixture is in contact with a gas containing oxygen from the substrate side A method of performing a polymerization curing step by performing ultraviolet irradiation and increasing the difference in polymerization rate in the thickness direction due to inhibition of oxygen polymerization by ultraviolet irradiation from the substrate side (Japanese Patent Application Laid-Open No. 2000-139953) is preferably used. It is done.

  Regarding the method described in JP-A-2000-13953, a cholesteric liquid crystal layer having a wider reflection wavelength band can be obtained by the following method.

For example, in the ultraviolet polymerization step, the liquid crystal mixture is in contact with a gas containing oxygen at an ultraviolet irradiation intensity of 20 to 200 mW / cm ² at a temperature of 20 ° C. or higher for 0.2 to 5 seconds. The step (1) of irradiating ultraviolet rays from the alignment substrate side, the step (2) of heating the liquid crystal layer at 70 to 120 ° C. for 2 seconds or more in a state where the liquid crystal layer is in contact with the gas containing oxygen, and then In the state in which the liquid crystal layer is in contact with a gas containing oxygen, the step of irradiating with ultraviolet rays from the alignment substrate side at a temperature of 20 ° C. or higher and lower than the step (1) for 10 seconds or more. (3) Next, there is a method performed by the step (4) of irradiating ultraviolet rays in the absence of oxygen (Japanese Patent Application No. 2003-93963).

Further, in the ultraviolet polymerization step, the liquid crystal mixture is in contact with a gas containing oxygen, at a temperature of 20 ° C. or higher, an ultraviolet irradiation intensity of 1 to 200 mW / cm ² and a range of 0.2 to 30 seconds. Step (1) of irradiating ultraviolet rays from the alignment substrate side three times or more while lowering the ultraviolet irradiation intensity and lengthening the ultraviolet irradiation time each time the number of times of ultraviolet irradiation increases, and then in the absence of oxygen Then, there is a method performed by the step (2) of irradiating with ultraviolet rays (Japanese Patent Application No. 2003-94307).

Further, the ultraviolet polymerization step is carried out for 0.2 to 5 seconds at an ultraviolet irradiation intensity of 20 to 200 mW / cm ² at a temperature of 20 ° C. or higher in a state where the liquid crystal mixture is in contact with a gas containing oxygen. Step (1) of irradiating ultraviolet rays from the alignment substrate side, and then in a state where the liquid crystal layer is in contact with a gas containing oxygen, until it reaches a temperature higher than Step (1) and 60 ° C. or higher, A step (2) of irradiating with ultraviolet rays from the alignment substrate side for 10 seconds or more at a temperature rising rate of 2 ° C./second or lower with an ultraviolet irradiation intensity lower than that in step (1), and then irradiating with ultraviolet rays in the absence of oxygen. An example is a method performed in the step (3) (Japanese Patent Application No. 2003-94605).

  Furthermore, the following method can be used. In the following method, a cholesteric liquid crystal layer having a wide reflection wavelength band and good heat resistance can be obtained. For example, there is a method in which a liquid crystal mixture containing a polymerizable mesogenic compound (a), a polymerizable chiral agent (b) and a photopolymerization initiator (c) is subjected to ultraviolet polymerization between two substrates (Japanese Patent Application 2003). No. 4346, Japanese Patent Application No. 2003-4101). Further, there is a method in which a polymerizable ultraviolet absorber (d) is further added to the liquid crystal mixture and ultraviolet polymerization is carried out between two substrates (Japanese Patent Application No. 2003-4298). Also, a method of applying a liquid crystal mixture containing a polymerizable mesogenic compound (a), a polymerizable chiral agent (b), and a photopolymerization initiator (c) on an alignment substrate and subjecting it to ultraviolet polymerization in an inert gas atmosphere (Japanese Patent Application No. 2003-4406).

The ultraviolet polymerization step is performed for 0.1 to 5 seconds at a temperature of 70 ° C. or higher and an ultraviolet irradiation intensity of 10 to 200 mW / cm ^{2 in} a state where the liquid crystal mixture is in contact with a gas containing oxygen. , Ultraviolet ray irradiation (1), and then a step (2) of heat treatment at 70 ° C. or higher for 0.1 to 5 seconds in a state where the liquid crystal layer is in contact with a gas containing oxygen, After step (1) and step (2), the step can be performed by step (3) in which ultraviolet rays are irradiated in the absence of oxygen. Preferably, the step (1) and the step (2) are repeated a plurality of times, and then the step (3) of ultraviolet irradiation is performed (Japanese Patent Application No. 2004-71158).

Further, in the ultraviolet polymerization step, the liquid crystal mixture is in contact with a gas containing oxygen at an ultraviolet irradiation intensity of 10 to 200 mW / cm ² at a temperature of 70 ° C. or higher for 0.01 to 5 seconds. , Ultraviolet irradiation step (1), and then the step (2) of heat-treating at 70 ° C. or more for a time exceeding 5 seconds in a state where the liquid crystal layer is in contact with a gas containing oxygen. After step 1) and step (2), it can be carried out by having step (3) of irradiating with ultraviolet rays in the absence of oxygen. Preferably, the step (1) and the step (2) are repeated a plurality of times, and then the step (3) of ultraviolet irradiation is performed (Japanese Patent Application No. 2004-168666).

  In addition, as a manufacturing method of a polarizing element (A2), the method of the said Japanese Patent Application No. 2003-93963 is preferable.

  The polymerizable mesogenic compound (a), polymerizable chiral agent (b) and the like that form the cholesteric liquid crystal layer will be described below. These materials are cholesteric liquid crystal layers whose pitch length is continuously changed in the thickness direction, and cholesteric to form a laminate. Any liquid crystal layer can be used.

  As the polymerizable mesogenic compound (a), those having at least one polymerizable functional group and having a mesogenic group composed of a cyclic unit or the like are preferably used. Examples of the polymerizable functional group include an acryloyl group, a methacryloyl group, an epoxy group, and a vinyl ether group. Among these, an acryloyl group and a methacryloyl group are preferable. Further, by using a compound having two or more polymerizable functional groups, a crosslinked structure can be introduced to improve durability. Examples of the cyclic unit serving as a mesogenic group include biphenyl, phenylbenzoate, phenylcyclohexane, azoxybenzene, azomethine, azobenzene, phenylpyrimidine, diphenylacetylene, diphenylbenzoate, and bicyclohexane. Cyclohexylbenzene, terphenyl and the like. In addition, the terminal of these cyclic units may have substituents, such as a cyano group, an alkyl group, an alkoxy group, a halogen group, for example. The mesogenic group may be bonded via a spacer portion that imparts flexibility. Examples of the spacer portion include a polymethylene chain and a polyoxymethylene chain. The number of repeating structural units forming the spacer portion is appropriately determined depending on the chemical structure of the mesogenic portion, but the repeating unit of the polymethylene chain is 0 to 20, preferably 2 to 12, and the repeating unit of the polyoxymethylene chain is 0 to 0. 10, preferably 1-3.

The molar extinction coefficient of the polymerizable mesogenic compound (a) is 0.1 to 500 dm ³ mol ⁻¹ cm ⁻¹ @ 365 nm, 10 to 30000 dm ³ mol ⁻¹ cm ⁻¹ @ 334 nm, and 1000 to 100,000 dm ^3. it is preferably a mol ^-1 m ^-1 @ 314nm. Those having the molar extinction coefficient have ultraviolet absorbing ability. The molar extinction coefficient is 0.1-50 dm ³ mol ^-1 cm ^-1 @ 365 nm, 50-10000 dm ³ mol ^-1 cm ^-1 @ 334 nm, 10000-50000 dm ³ mol ^-1 cm ^-1 @ 314 nm More preferred. Molar extinction coefficient is ^{0.1~10dm 3 mol -1 cm -1 @ 365nm} , a ^{1000~4000dm 3 mol -1 cm -1 @ 334nm} , at 30000~40000dm ³ mol ^-1 cm ^-1 @ 314nm More preferably. Molar extinction coefficient of ^{0.1dm 3 mol -1 cm -1 @ 365nm} , 10dm 3 mol -1 cm -1 @ 334nm, 1000dm 3 mol -1 cm -1 @ without stick 314nm smaller than sufficient polymerization rate difference It is difficult to increase the bandwidth. On the other ^{hand, 500dm 3 mol -1 cm -1 @} 365nm, 30000dm 3 mol -1 cm -1 @ 334nm, 100000dm 3 mol -1 cm -1 @ If 314nm greater than the polymerization curing to not proceed completely does not end There is. The molar extinction coefficient is a value measured from the absorbance at 365 nm, 334 nm, and 314 nm obtained by measuring the spectrophotometric spectrum of each material.

  The polymerizable mesogenic compound (a) having one polymerizable functional group is, for example, a general formula of the following chemical formula 1:

（式中、Ｒ₁〜Ｒ₁₂は同一でも異なっていてもよく、−Ｆ、−Ｈ、−ＣＨ₃、−Ｃ₂Ｈ₅または−ＯＣＨ₃を示し、Ｒ₁₃は−Ｈまたは−ＣＨ₃を示し、Ｘ₁は一般式（２）：
−（ＣＨ₂ＣＨ₂Ｏ）_a−（ＣＨ₂）_b−（Ｏ）_c−、を示し、Ｘ₂は−ＣＮまたは−Ｆを示す。但し、一般式（２）中のａは０〜３の整数、ｂは０〜１２の整数、ｃは０または１であり、かつａ＝１〜３のときはｂ＝０、ｃ＝０であり、ａ＝０のときはｂ＝１〜１２、ｃ＝０〜１である。）で表される化合物があげられる。

(In the formula, R _{1 to} R ₁₂ may be the same or different and represent —F, —H, —CH ₃ , —C ₂ H ₅ or —OCH ₃ , and R ₁₃ represents —H or —CH ₃ . X ₁ is represented by the general formula (2):
— (CH ₂ CH ₂ O) _a — (CH ₂ ) _b — (O) _c —, and X ₂ represents —CN or —F. In the general formula (2), a is an integer of 0 to 3, b is an integer of 0 to 12, c is 0 or 1, and when a = 1 to 3, b = 0 and c = 0. Yes, when a = 0, b = 1 to 12, and c = 0 to 1. ).

  Examples of the polymerizable chiral agent (b) include LC756 manufactured by BASF.

  The amount of the polymerizable chiral agent (b) is preferably about 1 to 20 parts by weight, preferably 3 to 7 parts by weight based on 100 parts by weight of the total of the polymerizable mesogenic compound (a) and the polymerizable chiral agent (b). The part is more suitable. The helical twisting force (HTP) is controlled by the ratio of the polymerizable mesogenic compound (a) and the polymerizable chiral agent (b). By setting the ratio within the above range, the reflection band can be selected so that the reflection spectrum of the obtained cholesteric liquid crystal film can cover the long wavelength region.

  The liquid crystal mixture usually contains a photopolymerization initiator (c). Various kinds of photopolymerization initiators (c) can be used without particular limitation. Examples thereof include Irgacure 184, Irgacure 907, Irgacure 369, Irgacure 651 and the like manufactured by Ciba Specialty Chemicals. The blending amount of the photopolymerization initiator is preferably about 0.01 to 10 parts by weight with respect to 100 parts by weight of the total of the polymerizable mesogenic compound (a) and the polymerizable chiral agent (b), and 0.05 to 5 parts by weight. The part is more suitable.

  As the polymerizable ultraviolet absorber (d), a compound having at least one polymerizable functional group and having an ultraviolet absorbing function can be used without any particular limitation. Specific examples of the polymerizable ultraviolet absorber (d) include RUVA-93 manufactured by Otsuka Chemical Co., and UVA935LH manufactured by BASF. The blending amount of the polymerizable ultraviolet absorber (d) is preferably about 0.01 to 10 parts by weight with respect to a total of 100 parts by weight of the polymerizable mesogenic compound (a) and the polymerizable chiral agent (b). 5 parts by weight is more preferred.

  In order to widen the bandwidth of the resulting cholesteric liquid crystal film, the mixture can be mixed with an ultraviolet absorber to increase the UV exposure intensity difference in the thickness direction. Further, the same effect can be obtained by using a photoreaction initiator having a large molar extinction coefficient.

  The mixture can be used as a solution. Solvents used in preparing the solution are usually halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, phenols such as phenol and parachlorophenol, benzene, toluene, Aromatic hydrocarbons such as xylene, methoxybenzene, 1,2-dimethoxybenzene, others, acetone, methyl ethyl ketone, ethyl acetate, tert-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene bricol monomethyl ether, diethylene glycol Dimethyl ether, ethyl cellosolve, butyl cellosolve, 2-pyrrolidone, N-methyl-2-pyrrolidone, pyridine, triethylamine, te Rahidorofuran, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, can be used acetonitrile, butyronitrile, carbon disulfide, cyclopentanone, cyclohexanone and the like. The solvent to be used is not particularly limited, but methyl ethyl ketone, cyclohexanone, cyclopentanone and the like are preferable. Although the concentration of the solution depends on the solubility of the thermotropic liquid crystalline compound and the final film thickness of the cholesteric liquid crystal film, it cannot be generally stated, but it is usually preferably about 3 to 50% by weight.

  It should be noted that the exemplified alignment substrate can also be used when a cholesteric liquid crystal layer whose pitch length continuously changes in the thickness direction is produced. A similar method can be adopted as the orientation method.

(1/2 wavelength plate (B))
Examples of the half-wave plate (B) include polyethylene naphthalate, polyethylene terephthalate, polycarbonate, norbornene resins represented by JSR Arton, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene and other polyolefins, polyarylate, Those obtained by uniaxially stretching a resin film such as polyamide, those obtained by improving the viewing angle characteristics by biaxially stretching, or those in which the nematic alignment state of the rod-like liquid crystal is fixed can be used.

  The half-wave plate (B) is preferably a broadband wavelength plate having a phase difference characteristic that functions as a substantially half-wave plate in the entire visible light region in order to align the optical characteristics of each color and suppress coloring. . This is because if the change in the retardation value for each wavelength is too large, a difference occurs in the polarization characteristics for each wavelength, which affects the shielding performance for each wavelength and is colored and visually recognized. Such a half-wave plate (B) has a maximum in-plane refractive index in the X-axis, a direction perpendicular to the X-axis in the Y-axis, a refractive index in each axial direction in nx, ny, and a thickness d ( nm), the front phase difference value at each wavelength in the light source wavelength band (420 to 650 nm): (nx−ny) × d is preferably within ½ wavelength ± 10%. The variation of the phase difference value within the light source wavelength band is preferably small, desirably within ± 7%, and more desirably within ± 5%.

  Such a half-wave plate (B) can give a phase difference equivalent to a half wavelength regardless of the wavelength of incident light by controlling different wavelength lamination characteristics by different axis lamination of different kinds of retardation plates or molecular design.

  A wider functioning wavelength band is better, but at least when the emission center wavelength of the light source is a cold cathode tube, blue is located at about 435 nm, green is at 545 nm, and red is at around 610 nm. Since light is emitted with a value width, it is desirable that the characteristics of the half-wave plate (B) function within a range of at least about 420 nm to 650 nm. Polyvinyl alcohol is representative as a material of a retardation plate having such characteristics, and as a material designed for molecular use for optics, a norbornene-based resin film represented by JSR Arton or Nippon Zeon Zeonore, Examples include Teijin Pure Ace WR.

  Further, it is more desirable that the half-wave plate (B) functions as a half-wave plate for obliquely incident light. Generally, a phenomenon occurs in which the phase difference value changes due to an increase in the optical path length of the half-wave plate with respect to an obliquely incident light beam, and deviates from the originally obtained phase difference value. In order to prevent this, it is preferable to use a half-wave plate (B) in which the retardation in the thickness direction is controlled to reduce the change in retardation relative to the change in angle. As a result, a phase difference equivalent to that of the vertically incident light can be imparted to the obliquely incident light.

  In general, an Nz coefficient is used as a control coefficient for the retardation value in the thickness direction. The Nz coefficient is defined by taking the direction in which the in-plane refractive index is maximum as the X axis, the direction perpendicular to the X axis as the Y axis, and the thickness direction of the film as the Z axis, and the refractive indexes in the respective axial directions as nx, ny, nz. , Nz = (nx−nz) / (nx−ny). In order to give a phase difference value equivalent to that of the normal incident light to the incident light from the oblique direction, −2.5 <Nz ≦ 1 is preferable. More preferably, −2 <Nz ≦ 0.5. A typical example of the retardation plate that has been controlled in the thickness direction is a NRZ film manufactured by Nitto Denko. Note that the method as shown in Patent Document 17 cannot prevent the secondary transmission in the oblique direction. This is because it is impossible to achieve both the development of the phase difference in the oblique direction and the suppression of the increase in the phase difference in the oblique direction. This is the advantage of the present invention.

  For example, a cholesteric liquid crystal layer (C1) is used as the circularly polarized reflective polarizer (C). The cholesteric liquid crystal layer (C1) preferably has the same spiral direction as the polarizing elements (A1) and (A2).

  The cholesteric liquid crystal layer (C1) preferably has a wide selective reflection bandwidth in order to function in the visible light region. The thickness is desirably 200 nm or more, more desirably 300 nm or more, and further desirably 400 nm or more. Specifically, it is preferable to cover a range of 400 to 600 nm. As the cholesteric liquid crystal layer (C1), the same ones as the polarizing elements (A1) and (A2) can be used. However, in the polarizing elements (A1) and (A2), the linearly polarized light component increases as the incident angle increases due to the influence of the cholesteric liquid crystal layer, and thus circularly polarized light cannot enter. Therefore, when the cholesteric liquid crystal layer (C1) having a reflection bandwidth of 200 nm or more is used, the front phase difference (normal direction) is λ / 8 or less, and the phase difference increases as the incident angle increases. It is preferable to use in combination with (C2). By the retardation layer (C2), the normal direction is circularly polarized light, and substantially circularly polarized light can be transmitted even when the incident angle is increased. Examples of the retardation layer (C2) include a negative C-plate and a positive C-plate.

  Further, as the circularly polarized reflective polarizer (C), a linearly polarized reflective polarizer (C3) and a quarter wavelength plate (C4) can be used. When the ¼ wavelength plate (C4) is used, circularly polarized light may become elliptically polarized light as the incident angle increases due to its Nz coefficient. For this reason, the Nz coefficient of the quarter wave plate (C4) is preferably close to 0.5. In general, the Nz coefficient of the quarter wave plate (C4) is preferably −1.5 <Nz <2 and more preferably 0 <Nz <1.

  One quarter wavelength plate (C4) can be used alone, or two or more wavelength plates can be used in combination. For example, a half-wave plate (C41) and a quarter-wave plate (C42) can be used. That is, by stacking the half-wave plate (C41) and the quarter-wave plate (C42), it can function as a quarter-wave plate. Refer to FIG. As a result, circularly polarized light can be transmitted at a wider viewing angle (circularly polarized light can be transmitted even when the incident angle is increased). At this time, the axis of the ½ wavelength plate (C41) is arranged so as to be substantially coaxial with the linearly polarized light reflection axis of the linearly polarized reflective polarizer (C3), and the ¼ wavelength plate (C42) is further arranged. Install at approximately 45 ° to the axis. In this case, the Nz coefficient of the half-wave plate (C41) is preferably 0.75, and the Nz coefficient of the quarter-wave plate (C42) is preferably close to 0.5. In general, the Nz coefficient of the half-wave plate (C41) is preferably −1.5 <Nz <2, more preferably 0 <Nz <1, and the Nz coefficient of the quarter-wave plate (C42). The coefficient is preferably -1 <Nz <2, more preferably 0 <Nz <1.5.

  As these circularly polarized reflective polarizers (C), those described in the sections of the circularly polarized reflective polarizer (a1) and the linearly polarized reflective polarizer (a2) can be used.

(Diffusion plate)
A diffuser plate that can scatter incident light rays and increase the light reuse efficiency can be used without particular limitation. As the light diffusing plate, a plastic film is known in which transparent particles having a refractive index different from that of the polymer are dispersed in a matrix polymer using a thermoplastic resin. In addition, a combination of a thermoplastic resin and a low molecular liquid crystal, a combination of a low molecular liquid crystal and a photocrosslinkable low molecular liquid crystal, or a combination of polyvinyl alcohol and a low molecular liquid crystal can be used. . Further, as the diffusion plate, those obtained by roughening the surface of the translucent resin plate, those obtained by phase separation of polymer blends having different refractive indexes, and the like are known.

  It is preferable to select a diffusion plate having a suitable haze value depending on the location of the diffusion plate. A plurality of diffusion plates can be used. When using two or more, what has a different haze value can be used. When the diffusing plate is arranged so as to be closer to the viewing side than the lenticular lens array, it is preferable to use a diffusing plate having a weak haze in order to prevent moiré with the liquid crystal panel. The scattering angle of the diffusion plate is preferably small. The scattering angle is preferably smaller than the half-value width with respect to the incident angle of the transmittance of the transmittance incident angle dependent optical element. This is because if the haze and scattering angle are large, the effect of narrowing the emission angle by the transmittance incident angle dependent optical element is lost. The diffusion plate preferably has a haze of 90% or less, and more preferably 80% or less in order to prevent unnecessary diffusion of the optical path.

(a reflector)
A reflector having a ridgeline and a repeated inclined structure can be used without particular limitation. In order to prevent the repeated inclined structure of the reflector from being visually recognized and to reduce the overall thickness, it is preferable that the pitch of the repeated inclined structure is sufficiently small. However, the pitch length is not particularly limited because the reflecting plate is disposed further below the linear light source and is also far from the liquid crystal panel. In order to reduce the overall thickness, the pitch length is 1 cm or less, more preferably 5 mm or less, and even more preferably 2 mm or less. As described above, the inclination angle of the inclined structure is preferably 5 to 40 degrees. However, when the inclination angle is around 30 degrees, the thickness increase due to the repetitive structure is about 1/2 of the inclined surface length. This is because when the pitch length is 1 cm, the thickness increase is 2.5 mm, and further increase in thickness is not preferable.

    As the repeated inclined structure of the reflecting plate, generally, an inclined surface as shown in FIG. 11 has a planar structure. Further, the inclined surface may be a curved surface. In order to prevent moiré with the liquid crystal display device, a random undulation structure as shown in FIG. 8 may be provided. Further, the ridgeline may have a slight angle with respect to the side direction of the liquid crystal display device.

  The production method of the reflector is not particularly limited, and various methods can be adopted. For example, a method of obtaining a shape transfer of a thermoplastic resin such as polycarbonate, polymethyl methacrylate, norbornene resin from a mold; using a UV curable resin on the surface of a transparent substrate such as polyethylene terephthalate or triacetyl cellulose. Method obtained by shape transfer; Method obtained by mask exposure using UV curable resin; Method obtained by etching treatment; Method of transferring mold shape using thermosetting resin such as epoxy resin; Stress applied to resin film And a method using a crazed structure having a surface shape and embossing a metal thin film such as a foamed polyethylene terephthalate film or an aluminum foil. Further, the surface of the reflecting material can be appropriately formed by vapor deposition thin film or rolled plate of high reflectivity metal such as aluminum, silver, chrome, stainless steel, etc., in addition to those caused by total reflection scattering such as foamed polyethylene terephthalate and barium sulfate. Thus, the manufacturing method and material of the reflector are not particularly limited.

(Lamination of each layer)
In the drawing, each member is individually arranged. As described above, each member may be simply stacked, but each layer can be laminated using an adhesive or a pressure-sensitive adhesive from the viewpoint of workability and light utilization efficiency.

  For example, when adjacent surfaces of each member are flat surfaces, a Newton ring (interference fringe) problem may occur. In order to prevent this, when the adjacent surfaces are flat surfaces, a method of bonding with an adhesive or a pressure-sensitive adhesive and eliminating the interface to improve the handling property is preferably used. Specifically, an acrylic light transmissive adhesive material (manufactured by Nitto Denko, No. 7 or the like) or an optical adhesive (for example, a UV curable adhesive material NOA60 series made by NORLAND, etc.) can be used.

  Moreover, isotropic scattering can be imparted to the adhesive or the pressure-sensitive adhesive as necessary by further adding particles for adjusting the degree of diffusion. In this case, the adhesive layer and the pressure-sensitive adhesive layer function as a diffusion layer (diffusion plate). In addition, an ultraviolet absorber, an antioxidant, a surfactant, and the like can be appropriately added to the adhesive and the pressure-sensitive adhesive for the purpose of imparting leveling properties during film formation, as necessary.

  In addition, when arranging each member without bonding, spacers are arranged around the stack so as to be arranged at an interval (2 μm or more) enough to prevent Newton rings, or 2 μm or more on the contact surface. A roughened layer having random irregularities can be provided.

(Liquid crystal display device)
The direct type backlight is suitably applied to a liquid crystal panel in which polarizing plates are arranged on both sides of a liquid crystal cell to form a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. The liquid crystal cell is not particularly limited, and any type of liquid crystal cell such as a TN type, STN type, or π type can be used.

(Other materials)
Note that the liquid crystal display device is manufactured by appropriately using various optical layers and the like according to a conventional method.

  The polarizing plates are disposed on both sides of the liquid crystal cell. The polarizing plates arranged on both sides of the liquid crystal cell are arranged so that the polarization axes are substantially orthogonal to each other. Further, the polarizing plate on the incident side is arranged so that the polarization axis direction thereof is aligned with the axial direction of linearly polarized light obtained by transmission from the light source side.

  In general, a polarizing plate having a protective film on one side or both sides of a polarizer is generally used.

  The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include hydrophilic polymer films such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. Examples thereof include polyene-based oriented films such as those obtained by adsorbing volatile substances and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic material such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution such as potassium iodide which may contain boric acid, zinc sulfate, zinc chloride and the like. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, or may be performed while dyeing, or may be performed with dyeing after iodine. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  As a material for forming the transparent protective film provided on one side or both sides of the polarizer, a material excellent in transparency, mechanical strength, thermal stability, moisture shielding property, isotropy and the like is preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, styrene such as polystyrene and acrylonitrile / styrene copolymer (AS resin) -Based polymer, polycarbonate-based polymer and the like. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Polymer blends and the like are also examples of polymers that form the transparent protective film. The transparent protective film can also be formed as a cured layer of thermosetting or ultraviolet curable resin such as acrylic, urethane, acrylurethane, epoxy, and silicone.

  Moreover, the polymer film described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a substitution in the side chain And / or a resin composition containing a thermoplastic resin having unsubstituted phenyl and a nitrile group. A specific example is a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used.

  Although the thickness of a protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable.

  Moreover, it is preferable that a protective film has as little color as possible. Therefore, Rth = [(nx + ny) / 2−nz] · d (where nx and ny are the main refractive index in the plane of the film, nz is the refractive index in the film thickness direction, and d is the film thickness). A protective film having a retardation value in the film thickness direction of −90 nm to +75 nm is preferably used. By using a film having a thickness direction retardation value (Rth) of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the protective film can be almost eliminated. The thickness direction retardation value (Rth) is more preferably −80 nm to +60 nm, and particularly preferably −70 nm to +45 nm.

  As the protective film, a cellulose polymer such as triacetyl cellulose is preferable from the viewpoints of polarization characteristics and durability. A triacetyl cellulose film is particularly preferable. In addition, when providing a protective film in the both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used. The polarizer and the protective film are usually in close contact with each other through an aqueous adhesive or the like. Examples of the water-based adhesive include an isocyanate-based adhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive, a vinyl-based latex, a water-based polyurethane, and a water-based polyester.

  The surface of the transparent protective film to which the polarizer is not adhered may be subjected to a hard coat layer, an antireflection treatment, an antisticking treatment, or a treatment for diffusion or antiglare.

  The hard coat treatment is applied for the purpose of preventing scratches on the surface of the polarizing plate. For example, a transparent protective film with a cured film excellent in hardness, sliding properties, etc. by an appropriate ultraviolet curable resin such as acrylic or silicone is used. It can be formed by a method of adding to the surface of the film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

  The anti-glare treatment is applied for the purpose of preventing the outside light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by a sandblasting method or an embossing method. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a blending method of transparent particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the transparent protective film itself, or can be provided separately from the transparent protective film as an optical layer.

  Examples of the optical layer include retardation plates such as quarter-wave plates and half-wave plates. For example, the quarter-wave plate changes the emitted circularly polarized light to linearly polarized light when the emitted light from the transmittance incident angle dependent optical element is circularly polarized light. As the quarter-wave plate, an appropriate retardation plate is used according to the purpose of use. The wavelength plate can be formed by stacking two or more kinds of retardation plates to control optical characteristics such as retardation. As the retardation plate, a birefringent film obtained by stretching a film made of an appropriate polymer such as polycarbonate, norbornene resin, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefins, polyarylate, polyamide, Examples thereof include an alignment film made of a liquid crystal material such as a liquid crystal polymer, and an alignment layer of the liquid crystal material supported by the film. The thickness of the wave plate is usually preferably from 0.5 to 200 μm, particularly preferably from 1 to 100 μm.

  A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region exhibits, for example, a retardation layer that functions as a quarter-wave plate for light-color light having a wavelength of 550 nm and other retardation characteristics. It can be obtained by a method of superposing a retardation layer, for example, a retardation layer functioning as a half-wave plate. Therefore, the retardation film may be composed of one or more retardation layers.

  The retardation plate is laminated on a polarizing plate as a viewing angle compensation film and used as a wide viewing angle polarizing plate. The viewing angle compensation film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen.

  As such a viewing angle compensation retardation plate, a birefringent film that has been biaxially stretched or stretched in two orthogonal directions, a bidirectionally stretched film such as a tilted orientation film, and the like are used. Examples of the inclined alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, and a film obtained by obliquely aligning a liquid crystal polymer. Can be mentioned. The viewing angle compensation film can be appropriately combined for the purpose of preventing coloring or the like due to a change in viewing angle based on a phase difference caused by a liquid crystal cell or increasing the viewing angle for good viewing.

  Also, from the point of achieving a wide viewing angle with good visibility, an optically compensated phase difference in which a liquid crystal polymer alignment layer, particularly an optically anisotropic layer composed of a discotic liquid crystal polymer gradient alignment layer, is supported by a triacetylcellulose film. A plate can be preferably used.

  In addition to the above, the optical layer laminated in practical use is not particularly limited. For example, one or more optical layers that may be used for forming a liquid crystal display device such as a reflective plate or a transflective plate are used. Can do. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a reflecting plate or a semi-transmissive reflecting plate is further laminated on an elliptical polarizing plate or a circular polarizing plate can be given.

  A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like as necessary.

  Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or vapor-deposited film made of a reflective metal such as aluminum on one surface of a protective film matted as necessary. In addition, the protective film may contain fine particles to form a surface fine concavo-convex structure and a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has an advantage that incident light is diffused by irregular reflection to prevent directivity and glaring appearance and to suppress unevenness in brightness and darkness. Moreover, the protective film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through it and light and dark unevenness can be further suppressed. The reflective layer with a fine concavo-convex structure reflecting the surface fine concavo-convex structure of the protective film is transparently protected by an appropriate method such as a vapor deposition method such as a vacuum deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of attaching directly to the surface of the layer.

  The reflective plate can be used as a reflective sheet in which a reflective layer is provided on an appropriate film according to the transparent film, instead of the method of directly imparting to the protective film of the polarizing plate. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a protective film, a polarizing plate or the like is used to prevent a decrease in reflectance due to oxidation, and thus the long-term sustainability of the initial reflectance. More preferable is the point of avoiding the additional attachment of the protective layer.

  The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device or the like that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate can be formed. In other words, the transflective polarizing plate is useful for forming a liquid crystal display device of a type that can save energy of using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source even in a relatively dark atmosphere. It is.

  Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers like the above-described polarization separation type polarizing plate. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above-mentioned reflective polarizing plate or transflective polarizing plate and a retardation plate are combined may be used.

  The polarizing plate and the retardation plate can be formed by sequentially laminating them separately in the manufacturing process of the liquid crystal display device. There is an advantage that the manufacturing efficiency of a liquid crystal display device and the like can be improved by being excellent in stability and laminating workability.

  The optical layer can be provided with an adhesive layer or an adhesive layer. The pressure-sensitive adhesive layer can be used for adhering to a liquid crystal cell and also used for laminating optical layers. When adhering the optical films, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.

  It does not restrict | limit especially as an adhesive agent or an adhesive. For example, acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyvinyl ether, vinyl acetate / vinyl chloride copolymer, modified polyolefin, epoxy-based, fluorine-based, natural rubber, synthetic rubber and other rubber-based polymers Can be appropriately selected and used. In particular, those excellent in optical transparency, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties and excellent in weather resistance, heat resistance and the like can be preferably used.

  The adhesive or pressure-sensitive adhesive can contain a crosslinking agent according to the base polymer. Examples of adhesives include natural and synthetic resins, in particular, tackifier resins, glass fibers, glass beads, metal powders, other inorganic powders, fillers, pigments, colorants, and antioxidants. An additive such as an agent may be contained. Further, it may be an adhesive layer containing fine particles and exhibiting light diffusibility.

  The adhesive and the pressure-sensitive adhesive are usually used as an adhesive solution having a solid content concentration of about 10 to 50% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent. As the solvent, an organic solvent such as toluene or ethyl acetate or a solvent such as water can be appropriately selected and used.

  The pressure-sensitive adhesive layer and the adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as an overlapping layer of different compositions or types. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 500 μm, preferably 5 to 200 μm, particularly preferably 10 to 100 μm.

  For the exposed surface such as the adhesive layer, a separator is temporarily attached and covered for the purpose of preventing contamination until it is put to practical use. Thereby, it can prevent contacting an adhesion layer in the usual handling state. As the separator, except for the above thickness conditions, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foam sheet, metal foil, laminate thereof, and the like, silicone type or Appropriate ones according to the prior art, such as those coated with an appropriate release agent such as a long mirror alkyl type, fluorine type or molybdenum sulfide, can be used.

  In the present invention, each layer such as the optical element or the adhesive layer is treated with an ultraviolet absorber such as a salicylic acid ester compound, a bezophenol compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound. It may also be one having an ultraviolet absorbing ability by a method such as

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is shown below and is not limited to the examples.

  Note that the front phase difference is defined by the direction in which the in-plane refractive index is maximized as the X axis, the direction perpendicular to the X axis as the Y axis, and the thickness direction of the film as the Z axis, and the refractive index in each axial direction as nx, As ny and nz, the refractive index nx, ny and nz at 550 nm were measured by an automatic birefringence measuring device (manufactured by Oji Scientific Instruments, automatic birefringence meter KOBRA21ADH), and the thickness d (nm) of the retardation layer. From the above, the front phase difference: (nx−ny) × d and the thickness direction phase difference: (nx−nz) × d were calculated. The phase difference when measured by tilting can be measured by the automatic birefringence measuring apparatus. The tilt phase difference is: (nx−ny) × d at the time of tilt.

  The Nz coefficient is defined by the formula: Nz = (nx−nz) / (nx−ny).

  The reflection wavelength band was determined by measuring the reflection spectrum with a spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., instantaneous multi-photometry system, MCPD-2000), and having a reflection wavelength band having a half of the maximum reflectance.

  The haze value was measured using a haze meter HM150 manufactured by Murakami Color Research Laboratory.

  The total light transmittance was measured with a spectrophotometer U4100 manufactured by Hitachi, Ltd.

  The front luminance was measured with a viewing angle measuring device (Ez-Contrast, manufactured by ELDIM).

  UVC321AM1 manufactured by USHIO INC. Was used as the ultraviolet exposure apparatus used for sample preparation.

Example 1
A high haze diffuser plate, a BEF sheet, and a low haze diffuser plate were removed from a commercially available product (sharp Aquos, 20-inch) backlight for TFT liquid crystal TV (cold cathode tube type). A conceptual diagram of the backlight is shown in FIG.

  Low haze diffuser: haze value of about 80%.

  BEF sheet: 3M BEF-III type.

  High haze diffusion plate: haze value of about 95%.

  Light source: cold cathode tube / five U-shaped linear light sources.

  Reflector: Foamed polyethylene terephthalate film.

  Above the light source, a lenticular lens obtained by placing an acrylic round bar (Takamasa Resin Co., Ltd., φ1 mm, total light transmittance of about 92%, no in-plane retardation, thickness of about 1 mm) on the film in parallel, The ridge line of the lenticular lens array and the long axis of the linear light source were arranged in parallel. As a result, the direct image of the cold-cathode tube diffused and appeared to be combined with the adjacent image.

  Next, a polarizing plate-retarder-cholesteric liquid crystal (reflective polarizer) integrated product (manufactured by Nitto Denko, SEG1425DU-PCF400) is attached to the upper surface side of the bandpass filter shown below. 7) and pasted together. The laminate was bonded to the band pass filter on the reflective polarizer side.

  The directions of the circularly polarized light reflected by the band pass filter and the PCF 400 are reversed. The bandpass filter is set to transmit the bright line spectrum, and the transmitted light of the bright line spectrum is natural light. Light other than the emission line spectrum is circularly polarized light. When the light that has passed through the bandpass filter reaches the PCF 400, the RGB bright line spectrum is separated into left and right circularly polarized light, one is transmitted and the other is reflected. On the other hand, all light other than the bright line spectrum is reflected. This effect is established in the vicinity of normal incidence. At oblique incidence, the characteristics of the bandpass filter shift to the short wavelength side, so that the RGB bright line light cannot be transmitted, all oblique incident light is reflected, and eventually only the front direction light is transmitted.

  The reflector directly under the light source is also removed, and instead of the reflector having an inclined structure (Toray Lumirror E60L, white PET) processed into an accordion shape with an inclination angle of 35 degrees and a pitch length of 5 mm, its ridgeline and linear shape The light sources were arranged so as to be orthogonal. The arrangement order of each member is the same as that in FIG. 1 except that the polarizing plate and the quarter wavelength plate are provided.

(Bandpass filter (1))
A bandpass filter was prepared by thin film coating of a cholesteric liquid crystal polymer. A three-wavelength bandpass filter for right circular polarization reflection and a broadband circular polarizing plate for left circular polarization reflection were combined. Only the intended three wavelengths are transmitted through circularly polarized light in the vicinity of the vertical direction, reverse circularly polarized light is reflected and recycled, and all obliquely incident light beams are reflected.

  Selective reflection circularly polarized bandpass filters that reflect right circularly polarized light in the selective reflection wavelength regions of 440 to 490 nm, 540 to 600 nm, and 615 to 700 nm with respect to the emission spectra of 435 nm, 535 nm, and 610 nm of the three-wavelength cold cathode tube were prepared.

  The liquid crystal materials used are three cholesteric liquid crystal polymers having selective reflection center wavelengths of 480 nm, 550 nm, and 655 nm based on EP0834754A1 as in Example 1. Cholesteric liquid crystal polymer

で表される重合性ネマチック液晶モノマーＡと、下記化３：

A polymerizable nematic liquid crystal monomer A represented by the formula:

で表される重合性カイラル剤Ｂを（ＥＰ０８３４７５４Ａ１とは鏡像対象）を下記に示す割合（重量比）
選択反射中心波長：モノマーＡ／カイラル剤Ｂ（配合比）
４８０ｎｍ： ９．８１／１
５５０ｎｍ： １１．９／１
６５５ｎｍ： １４． ８／１
で配合した液晶混合物を重合することにより作製した。

The following ratio (weight ratio) of the polymerizable chiral agent B represented by the formula (EP0834754A1 is a mirror image object)
Selective reflection center wavelength: monomer A / chiral agent B (mixing ratio)
480 nm: 9.81 / 1
550 nm: 11.9 / 1
655 nm: 14. 8/1
It was produced by polymerizing the liquid crystal mixture blended in 1.

  Each of the liquid crystal mixtures was made into a 33 wt% solution dissolved in tetrahydrofuran, and then purged with nitrogen in an environment of 60 ° C. to obtain a reaction initiator (azobisisobutyronitrile, 0.5 wt% based on the mixture). ) Was added for polymerization treatment. The resulting polymer was purified by reprecipitation separation with diethyl ether.

  The cholesteric liquid crystal polymer was dissolved in methylene chloride to prepare a 10% by weight solution. The solution was applied to the alignment substrate with a wire bar so that the thickness upon drying was about 1.5 μm. A 75 μm-thick polyethylene terephthalate (PET) film was used as the alignment substrate, and about 0.1 μm of a polyvinyl alcohol alignment film was applied to the surface and rubbed with a rayon rubbing cloth. After coating, it was dried at 140 ° C. for 15 minutes. After this heat treatment, the liquid crystal was cooled and fixed at room temperature to obtain a thin film.

  A cholesteric liquid crystal thin film of each color is produced through the same process, and after being bonded with an isocyanate-based adhesive (AD126 manufactured by Special Colorant Chemical Co., Ltd.), the operation of removing the PET substrate is repeated to shorten each cholesteric liquid crystal layer. Three layers were laminated in order from the wavelength side to obtain a cholesteric liquid crystal laminate (bandpass filter (1)) having a thickness of about 5 μm. The transmittance of the obtained cholesteric liquid crystal laminate is shown in FIG. The laminate of cholesteric liquid crystals had a distortion rate in the front direction of about 0.90 and a distortion rate in the 60 ° tilt direction of about 0.54.

Example 2
The high haze diffusion plate, the BEF sheet, and the low haze diffusion plate were removed from the same commercially available backlight for TFT liquid crystal TV (cold cathode tube type) as in Example 1.

  Above the light source, an AGS1-TAC film made by Nitto Denko (haze value of about 26%, in-plane retardation of 15 nm, thickness of about 85 mm) was disposed as a diffusion plate. In addition, a lenticular lens array manufactured by Edmund (on the other hand, a lens-like lens array, a lens pitch of 0.18 mm, a total light transmittance of about 92%, no in-plane retardation, and a thickness of about 2 mm) is placed with the lens surface facing upward. The array ridgeline and the long axis of the linear light source were arranged in parallel. The diffusion plate was bonded to the flat side of the lenticular lens array with an acrylic adhesive (Nitto Denko, No. 7). As a result, the direct image of the cold-cathode tube diffused and appeared to be combined with the adjacent image.

  Next, the optical elements shown below were arranged. Nitto Denko's polarizing plate (SEG1425DU) and Nitto Denko's phase difference plate (¼ wavelength plate, front phase difference of 140 nm, NRF 140) are coated with an acrylic adhesive (Nitto Denko, No. 7). A bonded circularly polarizing plate was placed.

  The reflective plate directly under the light source is also removed, and instead, barium sulfate (manufactured by Wako Pure Chemical Industries) is coated on a PMMA plate (mold transfer molding product) having a repetitive inclined structure with an inclination angle of 35 degrees and a pitch length of 1 mm. The resulting reflector was placed so that its ridgeline and the linear light source were orthogonal. The arrangement order of each member is the same as that shown in FIG.

  The optical element (1) was produced by the following method.

(Polarizing element (A1))
Five kinds of cholesteric liquid crystal polymers having selective reflection center wavelengths of 460 nm, 510 nm, 580 nm, 660 nm, and 800 nm were prepared based on the specification of European Patent Application No. 0837544.

The cholesteric liquid crystal polymer comprises a polymerizable nematic liquid crystal monomer A represented by the chemical formula 2 and a polymerizable chiral agent B represented by the chemical formula 3 in the following ratio (weight ratio).
Selective reflection center wavelength: monomer A / chiral agent B (combination ratio): selective reflection wavelength band (nm)
460 nm: 9.2 / 1: 430 to 490 nm
510 nm: 10.7 / 1: 480 to 550 nm
580 nm: 12.8 / 1: 540 to 620 nm
660 nm: 14.9 / 1: 620 to 810 nm
800 nm: 17/1: 700 to 900 nm
It was produced by polymerizing the liquid crystal mixture blended in 1.

  Each of the liquid crystal mixtures was made into a 33 wt% solution dissolved in tetrahydrofuran, and then purged with nitrogen in an environment of 60 ° C. to obtain a reaction initiator (azobisisobutyronitrile, 0.5 wt% based on the mixture). ) Was added for polymerization treatment. The resulting polymer was purified by reprecipitation separation with diethyl ether.

  The cholesteric liquid crystal polymer was dissolved in methylene chloride to prepare a 10% by weight solution. The solution was applied to the alignment substrate with a wire bar so that the thickness upon drying was about 1.5 μm. A 75 μm thick polyethylene terephthalate (PET) film was used as the alignment substrate, and a polyimide alignment film was applied to the surface of about 0.1 μm and rubbed with a rayon rubbing cloth. After coating, it was dried at 140 ° C. for 15 minutes. After this heat treatment, the liquid crystal was cooled and fixed at room temperature to obtain a thin film.

  Each color was overcoated on the obtained liquid crystal thin film through the same process, and the layers were sequentially laminated from the long wavelength side to the short wavelength side. As a result, an approximately 8 μm-thick cholesteric liquid crystal laminate in which each liquid crystal layer was laminated in order from the short wavelength side was obtained. The obtained cholesteric liquid crystal laminate was peeled off from the PET substrate. The obtained cholesteric liquid crystal laminate had a selective reflection function at 430 nm to 900 nm. This was designated as a polarizing element (A1).

  The polarizing element (A1) had a distortion rate in the front direction of about 0.55 and a distortion rate in the 60 ° inclination direction of about 0.05. Outgoing light transmitted through the polarizing element (A1) is linearly polarized light with a large incident angle, and the linearly polarized light has a polarization axis substantially perpendicular to the normal direction (front) of the polarizing element surface. Had.

(Polarizing element (A1 '))
In the polarizing element (A), the same operation is performed except that the enantiomer (B ′) is used in place of the polymerizable chiral agent B, and the circularly polarizing characteristic in the direction opposite to that of the polarizing element (A1) is obtained. A polarizing element (A1 ′) having the following was produced. The selective reflection wavelength bandwidth and distortion rate of the polarizing element (A1 ′) were almost the same as those of the polarizing element (A1-1). The direction of the polarization axis of the linearly polarized light emitted was the same.

(1/2 wavelength plate (B))
A polycarbonate retardation film (TR film) manufactured by Nitto Denko was used. The front retardation value was 270 nm, Nz = about 1.0, the thickness was 35 μm, the retardation value at 430 nm was about + 8%, and the retardation value at 650 nm was about −5%.

(Optical element (1))
A polarizing element (A1), a half-wave plate (B), and a polarizing element (A1 ′) are laminated in this order using an Nitto Denko acrylic adhesive (NO.7): 25 μm in thickness. 1) was obtained.

Example 3
The high haze diffusion plate, the BEF sheet, and the low haze diffusion plate were removed from the same commercially available backlight for TFT liquid crystal TV (cold cathode tube type) as in Example 1.

  Above the light source, an optical fiber made of polymethyl methacrylate (Esca made by Mitsubishi Rayon, CK40 type, φ1 mm) is placed in parallel on the acrylic substrate and bonded onto the acrylic substrate (total light transmittance of about 90). %, No in-plane retardation, and 1 mm thickness) were arranged so that the ridge line of the lenticular lens array and the major axis of the linear light source were parallel. As a result, the direct image of the cold-cathode tube diffused and appeared to be combined with the adjacent image.

  Furthermore, an NGS-TAC AGS1-TAC film (haze value of about 26%, in-plane retardation of 15 nm, thickness of about 85 mm) was disposed as a diffusion plate.

  Next, the optical element (2) shown below was bonded and integrated using an adhesive material (manufactured by Nitto Denko, No. 7). Nitto Denko's polarizing plate (SEG1425DU) and Nitto Denko's phase difference plate (¼ wavelength plate, front phase difference of 140 nm, NRF 140) are coated with an acrylic adhesive (Nitto Denko, No. 7). A bonded circularly polarizing plate was placed.

  It is also obtained by removing the reflection plate directly under the light source and coating a silver vapor deposition film on a polymethyl methacrylate plate (mold transfer molding product) having a repetitive inclined structure with an inclination angle of 35 degrees and a pitch length of 1 mm instead. The reflector was arranged so that the ridgeline and the linear light source were orthogonal. The arrangement order of each member is the same as that shown in FIG.

  The optical element (2) was produced by the following method.

(Polarizing element (A1))
Prepare 95.4 parts by weight of monofunctional mesogenic compound (manufactured by Takasago International Corporation, L42), 4.6 parts by weight of bifunctional polymerizable chiral agent (LC756 made by BASF) and 233 parts by weight of solvent (cyclopentanone). A coating solution (solid content 30 wt%) was prepared by adding 5 wt% of a photopolymerization initiator (Ciba Specialty Chemicals, Irgacure 369) to the blended solution. The coating solution was cast on a stretched PET film (alignment substrate) using a wire bar so that the thickness after drying was 10 μm, and the solvent was dried at 100 ° C. for 2 minutes. The obtained film was subjected to UV irradiation at 50 mW / cm ² for 0.5 seconds in an air atmosphere at 100 ° C. from the PET substrate side as a step (1). Next, as step (2), heat treatment was performed for 2 seconds in an air atmosphere at 100 ° C. without UV irradiation. Further, steps (1) and (2) were repeated. Thereafter, as step (3), UV irradiation was performed from the liquid crystal layer side at 60 mW / cm ² for 30 seconds in a nitrogen atmosphere at 50 ° C. to obtain a cholesteric liquid crystal layer having a selective reflection band of 420 to 900 nm. This was designated as a polarizing element (A1).

  The polarizing element (A1) had a distortion rate in the front direction of 0.76 and a distortion rate in the 60 ° inclination direction of 0.10. Outgoing light transmitted through the polarizing element (A1-1) is linearly polarized light with a large incident angle, and the linearly polarized light is polarized in a direction substantially orthogonal to the normal direction (front) of the polarizing element surface. Had an axis.

(Polarizing element (A2))
A solution containing 96.2 parts by weight of a monofunctional mesogen compound (manufactured by Takasago International Corporation, L42), 3.8 parts by weight of a bifunctional polymerizable chiral agent (LC756 made by BASF) and a solvent (cyclopentanone). A coating liquid (solid content 30% by weight) was prepared by adding 3% by weight of a photopolymerization initiator (Ciba Specialty Chemicals, Irgacure 907) to the solid content. The coating solution was cast on a stretched PET film (alignment substrate) using a wire bar so that the thickness after drying was 8 μm, and the solvent was dried at 100 ° C. for 2 minutes. The obtained film was irradiated with UV at 100 mW / cm 2 for 0.6 seconds in an air atmosphere at 40 ° C. from the PET substrate side. Subsequently, it heated at 90 degreeC for 2 minute (s), and also UV irradiation was performed for 20 second at 6 mW / cm < ² > at 90 degreeC by air atmosphere. Thereafter, UV irradiation was performed at 60 mW / cm ² for 30 seconds from the liquid crystal layer side in a nitrogen atmosphere at 50 ° C. to obtain a cholesteric liquid crystal layer having a selective reflection band of 550 to 1100 nm. This was designated as a polarizing element (A2).

  The polarizing element (A2) had a distortion rate in the front direction of 0.96 and a distortion rate in the 60 ° inclination direction of 0.02. Outgoing light transmitted through the polarizing element (A2) is linearly polarized light with a large incident angle, and the linearly polarized light has a polarization axis substantially parallel to the normal direction (front face) of the polarizing element surface. Had.

(Optical element (2))
The polarizing element (A1) and the polarizing element (B1) were laminated using an Nitto Denko acrylic adhesive (NO.7) with a thickness of 25 μm to obtain an optical element (2).

Comparative Example 1
A polarizing plate (manufactured by Nitto Denko, SEG1425DU) and a linearly polarized reflective polarizer (manufactured by 3M, DBEF) are acrylic on a low-haze diffuser plate for a commercially available TFT liquid crystal TV backlight (used in the examples). The laminate bonded with an adhesive (manufactured by Nitto Denko, No. 7) was placed so that the reflective polarizer was on the lower side.

Comparative Example 2
An integrated product of polarizing plate-retarding plate-cholesteric liquid crystal (reflective polarizer) on a low-haze diffusion plate of a commercially available TFT liquid crystal TV backlight (used in the examples) (Nitto Denko, SEG1425DU-PCF400) ) With the reflective polarizer on the bottom.

The front luminance (cd / cm ² ) of the direct type backlights obtained in the above examples and comparative examples was measured. The front brightness of Comparative Examples 1 and 2 was the same. Table 1 shows the front luminance ratio of the examples when the front luminance value of Comparative Examples 1 and 2 is 100.

表１に示す、反射偏光子を用いた直下型バックライトにおいて、光の利用効率が向上し輝度が向上している。

In the direct type backlight using the reflective polarizer shown in Table 1, the light use efficiency is improved and the luminance is improved.

It is an example of the schematic of the direct type | mold backlight of this invention. It is an example of the schematic of the direct type | mold backlight of this invention. It is an example of the schematic of the direct type | mold backlight of this invention. It is an example of the schematic of the direct type | mold backlight of this invention. It is an example of the schematic of the direct type | mold backlight of this invention. It is an example of the schematic of the direct type | mold backlight of this invention. It is an example of the schematic of the lenticular lens array of this invention. It is an example of the schematic of the lenticular lens array of this invention. It is an example of sectional drawing of the lenticular lens array of this invention. It is an example of sectional drawing of the lenticular lens array of this invention. It is an example of the schematic of the reflecting plate of this invention. It is an example of the schematic of the reflecting plate of this invention. It is an example of sectional drawing of the reflecting plate of this invention. It is an example of sectional drawing of the reflecting plate of this invention. It is an example of sectional drawing of the reflecting plate of this invention. It is an example of the schematic diagram of the conventional direct type | mold backlight. It is an example of the schematic diagram of the conventional direct type | mold backlight. It is an example of the schematic diagram of the conventional direct type | mold backlight. It is an example of the schematic diagram of the conventional direct type | mold backlight. It is an example of the schematic diagram of the conventional direct type | mold backlight. 3 is a diagram illustrating a transmission spectrum of a bandpass filter according to Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Linear light source 2 Lenticular lens array 3 Reflective polarizer 4 Reflector 5 Diffuser

Claims (12)

For linear light sources
A lenticular lens array having a plurality of parallel ridge lines is disposed on one side thereof, and a transmittance incident angle dependent optical element is disposed thereon, and the ridge line of the lenticular lens array is the long axis of the linear light source. Are arranged approximately parallel to
On the other side, a reflector having a ridge line and having a repetitive inclined structure is arranged so that the ridge line of the reflector and the long axis of the linear light source are substantially perpendicular to each other. Type backlight.   2. The direct type backlight according to claim 1, wherein a diffuser plate is further arranged on the side where the lenticular lens array and the optical element whose transmittance depends on the incident angle are arranged with respect to the linear light source. .   The direct type backlight according to claim 1 or 2, wherein an inclination angle of the inclined structure of the reflector is 5 to 40 degrees.   4. The bandpass filter according to claim 1, wherein the transmittance incident angle-dependent optical element is a band-pass filter that transmits the bright line spectrum of the light source at a specific incident angle and reflects it at other angles. Direct type backlight.   5. The direct type backlight according to claim 4, wherein the band-pass filter is a stretched product of a multilayer laminate of resin materials having different refractive indexes.   5. The direct type backlight according to claim 4, wherein the band-pass filter is a vapor-deposited multilayer thin film of inorganic oxides having different refractive indexes.   5. The direct type backlight according to claim 4, wherein the band-pass filter is a laminate of cholesteric liquid crystal layers.   8. The direct type backlight according to claim 7, wherein the laminated body of cholesteric liquid crystal layers has a central wavelength of selective reflection of three or more, and each selective reflection wavelength band does not overlap.   The direct-type backlight according to claim 1, wherein the transmittance incident angle-dependent optical element is a laminate of two or more reflective polarizers.   10. The direct type backlight according to claim 9, wherein the laminate of reflective polarizers is a laminate of broadband cholesteric liquid crystal layers in which two or more selective reflection wavelength bands overlap each other.   11. The direct type backlight according to claim 9, further comprising at least one retardation plate between layers of the laminate of the reflective polarizers. A liquid crystal display device using the direct type backlight according to claim 1.

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