JPWO2016088787A1 - Liquid crystal display - Google Patents

Abstract

According to the present invention, there is provided a liquid crystal display device (51) comprising a display side polarizing plate (44), a liquid crystal cell (42), a backlight side polarizing plate (1), and a backlight unit (31) in this order, A brightness enhancement film (11) is included between the backlight side polarizing plate (1) and the backlight unit (31), and the brightness enhancement film (11) is from the backlight side polarizing plate (1) side. A λ / 4 plate (12) and a reflective polarizer (13) are included in this order, and the reflective polarizer (13) includes a light reflective layer (14a, 14b) formed by fixing at least one cholesteric liquid crystal phase. In addition, the liquid crystal display device (51) in which the chromaticity a * of the image light at the time of white display of the liquid crystal display device (51) is -3 <a * <14 in all azimuth angles of polar angles 0 ° to 60 °. ) Is provided. In the liquid crystal display device (51) of the present invention, the front luminance is high and the oblique color change is suppressed.

Description

  The present invention relates to a liquid crystal display device. More particularly, the present invention relates to a liquid crystal display device having high luminance and an adjusted oblique color change.

  Flat panel displays such as liquid crystal display devices (hereinafter also referred to as LCDs) have low power consumption and are increasingly used as space-saving image display devices year by year. For large-size LCDs, development of next-generation high-definition (4K2K, EBU ratio of 100% or more) of the current TV standard (FHD, NTSC (National Television System Committee) ratio 72% ≒ EBU (European Broadcasting Union) ratio 100%) Development for power saving, high definition, and improvement of color reproducibility is required not only for small-sized LCDs such as tablet PCs and smartphones, but also for large-sized LCDs.

  In a liquid crystal display device having a basic configuration in which a backlight, a backlight side polarizing plate, a liquid crystal cell, and a display side polarizing plate are provided in this order for power saving, between the backlight and the backlight side polarizing plate. It has been proposed to provide a reflective polarizing element. The reflective polarizing element is an optical element that transmits only light oscillating in a specific polarization direction among light incident while oscillating in all directions, and reflects light oscillating in other polarization directions. As the core component of low-power LCDs due to the increase in mobile devices and low power consumption of home appliances, it is expected to solve the low light efficiency of LCDs and increase the brightness (degree of brightness per unit area of light source). ing.

  As an example of the reflective polarizing element, Patent Document 1 discloses a reflective polarizing plate having a structure in which a layer formed by fixing a λ / 4 plate and a cholesteric liquid crystal phase is laminated, and a cholesteric liquid crystal phase having three or more layers having different cholesteric liquid crystal phase pitches. A technique for improving the light utilization rate of the backlight by light recycling by widening the reflection band by the layer formed by fixing the light is described.

  On the other hand, with the high definition of pixels as described above, the effect of deviation between the electrode pixel and the black matrix due to the bonding accuracy of the components in the liquid crystal display device is likely to occur, so without adopting the multi-domain method, Increasing light utilization is also being considered.

JP-A-1-133003 Japanese Patent No. 3518660

  However, when a reflective polarizing plate having a structure in which a λ / 4 plate and a layer in which a cholesteric liquid crystal phase is fixed is stacked is incorporated in a liquid crystal display device, the oblique polarization caused by the optical characteristics of the cholesteric liquid crystal phase and the λ / 4 plate. It is known that a color change (also referred to as color unevenness) is likely to occur when viewed from the direction. In particular, in a high-definition liquid crystal display device, the multi-domain method may not be adopted as described above, and orientation dependency in the liquid crystal driving state is more likely to be a problem, and a technique for correcting the color tone is required.

  The problem to be solved by the present invention is to provide a liquid crystal display device in which front luminance is high and oblique color change is suppressed.

Therefore, the present inventors have further studied the configuration of the brightness enhancement film and completed the present invention.
That is, the present invention provides the following [1] to [16].
[1] A liquid crystal display device including a display side polarizing plate, a liquid crystal cell, a backlight side polarizing plate, and a backlight unit in this order,
Including a brightness enhancement film between the backlight side polarizing plate and the backlight unit,
The brightness enhancement film includes a λ / 4 plate and a reflective polarizer in this order from the backlight side polarizing plate side,
The reflective polarizer includes a light reflection layer formed by fixing at least one cholesteric liquid crystal phase,
The liquid crystal display device in which the chromaticity a ^* of image light during white display of the liquid crystal display device is −3 <a ^* <14 in all azimuth angles of polar angles of 0 ° to 60 °.
[2] One or more selected from the group consisting of the display-side polarizing plate and the backlight-side polarizing plate is a polarizing plate having a hue chromaticity of a ^* > 0 when transmitted through a C light source. The liquid crystal display device according to [1].
[3] The liquid crystal display device according to [1] or [2], wherein the backlight unit has a front chromaticity of a ^* > 8.
[4] The liquid crystal according to any one of [1] to [3], wherein the reflective polarizer includes a light reflecting layer that reflects blue light and green light, and a red light reflecting layer that reflects red light. Display device.

[5] The liquid crystal display device according to [4], wherein the layer reflecting blue light and green light is a broadband light reflecting layer.
[6] The liquid crystal display device according to [4] or [5], wherein the red light reflection layer is a light reflection layer that further reflects infrared light.
[7] The liquid crystal according to any one of [1] to [3], wherein the reflective polarizer includes a light reflecting layer that reflects green light and red light, and a blue light reflecting layer that reflects blue light. Display device.
[8] The liquid crystal display device according to [7], wherein the layer reflecting green light and red light is a broadband light reflecting layer.
[9] The reflective polarizer includes a layer formed from a polymerizable liquid crystal composition containing a rod-like liquid crystal compound,
The spiral pitch of the cholesteric liquid crystal phase of the said layer formed from the polymeric liquid crystal composition containing a rod-shaped liquid crystal compound is changing continuously in the film thickness direction of the said layer. Liquid crystal display device.
[10] The liquid crystal display device according to any one of [1] to [9], wherein the reflective polarizer includes a layer formed from a polymerizable liquid crystal composition including a discotic liquid crystal compound.
[11] The liquid crystal display device according to any one of [1] to [10], wherein the λ / 4 plate is a layer formed from a polymerizable liquid crystal composition containing a discotic liquid crystal compound.
[12] The reflective polarizer includes a layer that changes a polarization state of light on a side opposite to the λ / 4 plate side, and the layer that changes the polarization state of light satisfies the following conditions [1] to [ The liquid crystal display device according to any one of 11].
0 <| average refractive index of the layer that changes the polarization state of light−average refractive index of the outermost light reflecting layer | <0.8

[13] The backlight unit is
Blue light having an emission center wavelength in a wavelength band of 430 to 500 nm;
Green light having an emission center wavelength in a wavelength band of 500 to 600 nm;
A light source that emits red light having at least a part of a peak of emission intensity in a wavelength band of 600 to 700 nm;
The backlight unit includes a reflecting member that converts and reflects the polarization state of light emitted from the light source and reflected by the brightness enhancement film or the optical sheet member at a rear portion of the light source. 12]. The liquid crystal display device according to any one of [12].
[14] The liquid crystal display device according to [13], wherein the full widths at half maximum of the blue light, green light, and red light are all 100 nm or less.
[15] The light source is a light source having a blue light emitting diode that emits the blue light and a fluorescent material that emits the green light and the red light when the blue light of the blue light emitting diode is incident. 13] or the liquid crystal display device according to [14].
[16] The liquid crystal display device according to [15], wherein the fluorescent material is a quantum dot member.

  According to the present invention, it is possible to provide a liquid crystal display device with high luminance and suppressed oblique color change.

It is a figure which shows the example of a layer structure of a brightness improvement film. It is one aspect of the layer configuration of the optical sheet member. It is a schematic sectional drawing of the example of the liquid crystal display device of this invention.

Hereinafter, the present invention will be described in detail.
The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In the present specification, the “half width” of a peak means the width of the peak at a peak height of 1/2.
The reflection center wavelength and half width of the light reflection layer can be obtained as follows.
When the transmission spectrum of the light reflection layer is measured using a spectrophotometer UV3150 (Shimadzu Corporation), a peak of decrease in transmittance is observed in the selective reflection region. Of the two wavelengths having a transmittance of 1/2 the maximum peak height, the wavelength value on the short wave side is λ1 (nm) and the wavelength value on the long wave side is λ2 (nm). The reflection center wavelength and the half width can be expressed by the following formula.
Reflection center wavelength = (λ1 + λ2) / 2
Half width = (λ2−λ1)

  In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at the wavelength λ, respectively. The unit is nm. Re (λ) is measured with KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments Co., Ltd.) by making light having a wavelength of λ nm incident in the normal direction of the film. In selecting the measurement wavelength λnm, the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like. When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method. This measuring method is also partially used for measuring the average tilt angle on the alignment layer side of the discotic liquid crystal molecules in the optically anisotropic layer, which will be described later, and the average tilt angle on the opposite side.

  Rth (λ) is Re (λ) with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotation axis) (in the absence of the slow axis, in-film plane) Measure the light at a wavelength of λnm from each tilted direction in steps of 10 degrees from the normal direction to 50 ° on one side with respect to the film normal direction. KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed value of the average refractive index, and the input film thickness value. In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing its sign to negative. The retardation value is measured from two inclined directions with the slow axis as the tilt axis (rotation axis) (if there is no slow axis, the arbitrary direction in the film plane is the rotation axis). Rth can also be calculated from the following formula (A) and formula (B) based on the value, the assumed value of the average refractive index, and the input film thickness value.

Note that Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction. In the formula (A), nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction orthogonal to nx in the plane, and nz is the direction orthogonal to nx and ny. Represents the refractive index. d is the film thickness.
Rth = ((nx + ny) / 2−nz) × d (B)

  When the film to be measured is a film that cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film without a so-called optical axis, Rth (λ) is calculated by the following method. Rth (λ) is −50 ° with respect to the normal direction of the film, with Re (λ) described above being the in-plane slow axis (determined by KOBRA 21ADH or WR) and the tilt axis (rotating axis). Then, 11 points of light having a wavelength of λ nm are incident in 10 ° steps from 1 ° to + 50 °, and the measured retardation value, average refractive index assumption and input film thickness value are used as the basis. KOBRA 21ADH or WR is calculated. In the above measurement, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. If the average refractive index is not known, it can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). The KOBRA 21ADH or WR calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

In the light reflection layer formed by fixing the cholesteric liquid crystal phase, when the normal ordinary refractive index no and the extraordinary refractive index ne of the liquid crystal are used, the average value of the in-plane refractive index is (nx + ny) / 2 = (no + ne) / 2
It is represented by
Further, since the refractive index in the film thickness direction is no, Rth of the light reflecting layer formed by fixing the cholesteric liquid crystal phase can be expressed by the following formula. Rth of the first light reflecting layer and the second light reflecting layer of the brightness enhancement film adopts a value calculated using the following formula, and the first light reflecting layer and the second light reflecting at the wavelength λ nm. The Rth of the layer is described as Rth (λ).
Rth = {(no + ne) / 2−no} × d = {(ne−no) / 2} × d
Note that ne and no can be measured with an Abbe refractometer.

Further, as a method for obtaining Rth of the cholesteric liquid crystal layer, a method using a polarization ellipso can be applied.
For example, M.M. Kimura et al. Jpn. J. et al. Appl. Phys. 48 (2009) When the ellipsometry method is used as described in 03B021, the thickness, pitch, twist angle, etc. of the cholesteric liquid crystal layer can be obtained, and the value of Rth can be obtained therefrom.

In this specification, “visible light” means light having a wavelength of 380 nm to 780 nm. Moreover, in this specification, when there is no special mention about a measurement wavelength, a measurement wavelength is 550 nm.
In this specification, blue light is light having a wavelength of 380 to 499 nm, green light is light having a wavelength of 500 to 599 nm, and red light is light having a wavelength of 600 to 780 nm. Infrared light is 780-850 nm light.

  Further, in the present specification, regarding the angle (for example, an angle such as “90 °”) and the relationship (for example, “orthogonal”, “parallel”, “crossing at 45 °”, etc.), the technical field to which the present invention belongs. The range of allowable error is included. For example, it means that the angle is within the range of strict angle ± 10 °, and the error from the strict angle is preferably 5 ° or less, and more preferably 3 ° or less.

In this specification, the “absorption axis” and “transmission axis” of a polarizer or a polarizing plate mean directions that form an angle of 90 ° with each other.
In the present specification, the “slow axis” of a retardation film or the like means a direction in which the refractive index is maximized.
Further, in this specification, numerical values, numerical ranges, and qualitative expressions (for example, “equivalent”, “equal”, etc.) indicating optical characteristics of each member such as a retardation region, a retardation film, and a liquid crystal layer are used. ) Is interpreted to indicate numerical values, numerical ranges and properties including generally allowable errors for liquid crystal display devices and members used therefor.
Further, in this specification, “front” means a direction normal to the image display surface of the liquid crystal display device.
In this specification, a reflective polarizer and a polarizer are used separately.

<Liquid crystal display device>
The liquid crystal display device includes a display side polarizing plate, a liquid crystal cell, a backlight side polarizing plate, and a backlight unit in this order. The liquid crystal display device of the present invention has a brightness enhancement film between the backlight side polarizing plate and the backlight unit.
One embodiment of a liquid crystal display device has a liquid crystal cell in which a liquid crystal layer is sandwiched between substrates on which electrodes are provided on at least one opposite side, and the liquid crystal cell is arranged between two polarizing plates. It is. The liquid crystal display device includes a liquid crystal cell in which liquid crystal is sealed between upper and lower substrates, and can display an image by changing the alignment state of the liquid crystal by applying a voltage. Furthermore, you may have a polarizing plate protective film and the retardation film for viewing angle compensation as needed. The retardation film for viewing angle compensation may be included between each of the polarizers and the liquid crystal cell. In addition, the liquid crystal display device of the present invention includes, for example, a color filter substrate, a thin layer transistor substrate, a lens film, a diffusion sheet, a hard coat layer, an antireflection layer, a low reflection layer, an antiglare layer, and the like (or in place thereof), Other members such as a forward scattering layer, a primer layer, an antistatic layer, and an undercoat layer may be included.

FIG. 3 shows an example of the configuration of the liquid crystal display device. In FIG. 3, the liquid crystal display device 51 includes a backlight unit 31, an optical sheet member 21 (a laminated body of the reflective polarizer 11 and the backlight side polarizing plate 1), a thin layer transistor substrate 41, a liquid crystal cell 42, and a color filter substrate. 43 and the display side polarizing plate 44 are laminated in this order.
In addition, in FIG. 3, the structure of a brightness improvement film is an example, for example, the brightness improvement film applied to a liquid crystal display device is not limited to the example as described in FIG.

  There is no restriction | limiting in particular about the structure of a liquid crystal cell, The liquid crystal cell of a general structure is employable. The liquid crystal cell includes, for example, a pair of substrates arranged opposite to each other and a liquid crystal layer sandwiched between the pair of substrates, and may include a color filter layer, if necessary. The driving mode of the liquid crystal cell is not particularly limited, and is twisted nematic (TN), super twisted nematic (STN), vertical alignment (VA), in-plane switching (IPS), optically compensated bend cell (OCB). Various modes such as can be used.

<Chromaticity a ^* of image light of liquid crystal display device>
In the liquid crystal display device of the present invention, the chromaticity a ^* of the image light at the time of white display is −3 <a ^* <14 at all polar angles of 0 ° to 60 °.
In this specification, the polar angle means an angle with respect to the image display direction of the normal line of the image display surface of the liquid crystal display device, and is an angle of 0 ° or more and 90 ° or less. The azimuth angle means an angle expressed by setting a rotation angle around the normal line of the image display surface to 0 ° in a specific direction, and is an angle between 0 ° and less than 360 °. In the present specification, image light means light emitted from the image display surface of a liquid crystal display device, and emits light in the backlight unit. At least the backlight side polarizing plate, the brightness enhancement film, the liquid crystal cell, and the display It means light emitted from the image display surface of the liquid crystal display device via the side polarizing plate.

The chromaticity a ^* is a chromaticity represented by coordinates in the CIE1976 (L ^* a ^* b ^* ) color space, which is an international standard. The CIE1976 (L ^* a ^* b ^* ) color space is also adopted in the Japanese Industrial Standard JIS 8781-4 created based on ISO 11664-4. The chromaticity a ^* can be obtained with a measuring instrument such as EZ-Contrast 160 manufactured by ELDIM, which is also used in the following examples. Redness increases as the value of the chromaticity a ^* is larger than 0, can be considered as the value of the chromaticity a ^* is increasing greenness as less than 0.

The present inventors use the brightness enhancement film in the process of improving the brightness of the liquid crystal display device using a brightness enhancement film including a light reflection layer formed by fixing a cholesteric liquid crystal phase as described below. It has been found that the sensory evaluation results are poor when the image of the liquid crystal display device is observed from an oblique direction. As a result of intensive studies, the configuration was adjusted so that the chromaticity a ^* was −3 <a ^* <14, and a liquid crystal display device with good sensory evaluation results was obtained. Although not bound by any theory, the color produced by the use of the brightness enhancement film is green, and the color tends to be unpleasant for the observer, so that the sensory evaluation result is good by bringing the color to red. It is thought that it became. By setting the chromaticity a ^{* to} be −3 <a ^* <14, it is difficult to identify a change in color even if there is a slight change in b ^*. It is done.

The chromaticity a ^* in all azimuth angles of the polar angle 0 ° to 60 ° is preferably −2 <a ^* <12, more preferably −1 <a ^* <11, and 0 <a ^*. More preferably, it is <10. In addition, the difference between the maximum value and the minimum value of the chromaticity a ^* at all polar angles of 0 ° to 60 ° is preferably 15 or less, more preferably 12 or less, and 10 or less. Further preferred.
In particular, the chromaticity a ^* is preferably −3 or more at all polar angles of 60 °, more preferably −2 or more, further preferably −1 or more, and 0 or more. It is particularly preferred.

The method for adjusting the configuration of the liquid crystal display device so that the chromaticity a ^* in all azimuth angles of polar angles 0 ° to 60 ° is −3 <a ^* <14 is not particularly limited. There are two types of methods.

The first method can be performed by controlling one or more colors selected from a display side polarizing plate and a backlight side polarizing plate. For example, it is preferable to perform the above color control using a polarizing plate whose absorbance is lower in the wavelength range of red light than in the wavelength range of blue light and the wavelength range of green light. The polarizing plate is configured to transmit green complementary color, which is a color generated by using the brightness enhancement film, and can achieve the chromaticity a ^* of −3 <a ^* <14 as the image light of the liquid crystal display device. It is. The absorbance of the polarizing plate in the red light wavelength region is 90% or less, 80% or less, with respect to the average value of the blue light wavelength region absorption maximum and the green light wavelength region absorption maximum. Alternatively, it may be 70% or less. Such a color control can be achieved by adjusting the amount of iodine ions used in the production of a polarizing plate using a polarizer obtained by adsorbing and orienting iodine on a polymer film described later. For example, if the concentration of potassium potassium is set higher than usual in the cleaning process using potassium potassium during the preparation of the polarizing plate, iodine ions in the polarizing plate decrease, and absorption on the long wavelength side (red) is more than that of the normal polarizing plate. It is possible to reduce. The color control may be performed with the display side polarizing plate, the backlight side polarizing plate, or both.

  The second method can be performed by controlling the emission color of the backlight unit. For example, the red light emission intensity of the backlight unit may be adjusted to be larger than the red light emission intensity of the normal backlight unit. With this configuration, green, which is a color generated by using the brightness enhancement film, can be complemented. For example, the red light emission intensity of the backlight unit may be adjusted to 110%, 120%, 130% or more of the green light emission intensity. As the adjustment method, for example, in a backlight unit, a blue light emitting diode, a wavelength conversion member including a fluorescent material that emits green light and a fluorescent material that emits red light when blue light from the blue light emitting diode is incident are provided. In the case of using the light source having, it is possible to increase the fluorescent material emitting red light more than usual.

<Brightness enhancement film>
The brightness enhancement film has a λ / 4 plate and a reflective polarizer. The reflective polarizer includes at least one light reflecting layer formed by fixing a cholesteric liquid crystal phase. An example of the layer structure of the brightness enhancement film is shown in FIG.
When the brightness enhancement film is incorporated in a liquid crystal display device, the brightness enhancement film improves the brightness of the liquid crystal display device by the following mechanism.
The light reflecting layer formed by fixing the cholesteric liquid crystal phase contained in the reflective polarizer in the brightness enhancement film has at least one of right circularly polarized light and left circularly polarized light (circularly polarized light in the first polarization state) having a reflection center wavelength. Reflects in the nearby wavelength band and transmits the other (circularly polarized light in the second polarization state). The reflected circularly polarized light in the second polarization state is randomized in its direction and polarization state by a reflection member (also referred to as a light guide or an optical resonator), which will be described later, and is recycled. Again, part of the light is reflected as circularly polarized light in the first polarization state, and the remaining part of light is transmitted as circularly polarized light in the second polarization state. Can be improved.
The light emitted from the reflective polarizer, that is, the polarization state of the transmitted light and the reflected light of the reflective polarizer can be measured, for example, by measuring the polarization with an Axoscan from Axometrics.

<Λ / 4 plate>
The brightness enhancement film has a λ / 4 plate.
The λ / 4 plate has an in-plane retardation Re (λ) at a specific wavelength λnm. Re (λ) = λ / 4
An optically anisotropic layer satisfying the above. In the brightness enhancement film, the λ / 4 plate functions as a layer for converting circularly polarized light obtained by passing through the reflective polarizer into linearly polarized light.
The λ / 4 plate preferably satisfies at least one of the following formulas (A) to (C), and more preferably satisfies all of the following formulas (A) to (C).
Formula (A) 450 nm / 4-35 nm <Re (450) <450 nm / 4 + 35 nm
Formula (B) 550 nm / 4-35 nm <Re (550) <550 nm / 4 + 35 nm
Formula (C) 630 nm / 4-35 nm <Re (630) <630 nm / 4 + 35 nm
(In the formulas (A) to (C), Re (λ) represents retardation in the in-plane direction (unit: nm) at the wavelength λ nm.)
By adjusting Rth of the λ / 4 plate, it is possible to cancel the phase difference in the thickness direction of the light reflection layer that occurs when viewed from an oblique direction.
Rth (550) of the λ / 4 plate is preferably −120 to 120 nm, more preferably −80 to 80 nm, and particularly preferably −70 to 70 nm.

As a method for manufacturing the λ / 4 plate, for example, a method described in JP-A-8-271731 can be used. The λ / 4 plate may be a single layer or a laminate of two or more layers, and is preferably a laminate of two or more layers. In particular, the λ / 4 layer is a liquid crystal compound (discotic liquid crystal) formed by polymerizing a liquid crystal monomer that expresses a retardation film (optically approximately uniaxial or approximately biaxial), a nematic liquid crystal layer, or a smectic liquid crystal layer. More preferably, the retardation film has one or more layers including at least one of a rod-like liquid crystal and a cholesteric liquid crystal. Regarding the retardation film, it is possible to select a retardation film stretched in the direction perpendicular to the conveyance direction or the conveyance direction during production of the support, and a retardation film stretched by 45 degrees with respect to the conveyance direction. A phase difference film obtained by stretching a cyclic polyolefin resin (norbornene-based resin) or the like capable of producing an optical sheet member by so-called roll-to-roll, or a transparent film is subjected to orientation treatment, and the treated surface is conveyed in the direction of production. On the other hand, a film having a layer in which a liquid crystal compound is oriented in a 45-degree direction is preferable. At this time, when a transparent substrate having a positive Rth is used, it is preferable to use a discotic liquid crystal compound in which the Rth is negative in an aligned state.
Hereinafter, the material and manufacturing method of the λ / 4 plate will be described in detail.

  There is no restriction | limiting in particular about the material used for (lambda) / 4 board which a brightness improvement film has. Various polymer films such as cellulose acylate, polycarbonate polymer, polyester polymer such as polyethylene terephthalate and polyethylene naphthalate, acrylic polymer such as polymethyl methacrylate, polystyrene, acrylonitrile / styrene copolymer (AS resin), etc. Styrene polymers and the like can be used. Polyolefins such as polyethylene and polypropylene, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers, polyethersulfone polymers , Polyetheretherketone polymers, polyphenylene sulfide polymers, vinylidene chloride polymers, vinyl alcohol polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers, epoxy polymers, or polymers obtained by mixing the aforementioned polymers One or two or more polymers are selected from the above, and a polymer film is produced using the polymer as a main component, and can be used for producing an optical film in a combination that satisfies the above characteristics. Kill.

  The λ / 4 plate may be an optically anisotropic support having the desired λ / 4 function by itself, or having an optically anisotropic layer on a support made of a polymer film. May be.

  When the λ / 4 plate is an optically anisotropic support having the desired λ / 4 function by the support itself, for example, the optical anisotropic support is achieved by a method of stretching a polymer film uniaxially or biaxially. You can get a body. There is no particular limitation on the type of the polymer, and those having excellent transparency are preferably used. Examples thereof include materials used for the above-mentioned λ / 4 plate, cellulose acylate films (for example, cellulose triacetate film (refractive index 1.48), cellulose diacetate film, cellulose acetate butyrate film, cellulose acetate propio). Nate film), polyolefins such as polyethylene and polypropylene, polyester resin films such as polyethylene terephthalate and polyethylene naphthalate, polyether sulfone films, polyacrylic resin films such as polymethyl methacrylate, polyurethane resin films, polyester films, polycarbonate films , Polysulfone film, polyether film, polymethylpentene film, polyetherketone film, (meth) acrylic Nitrile film, polyolefin, a polymer having an alicyclic structure (norbornene resin (ARTON, trade name, manufactured by JSR Corp.), amorphous polyolefin (ZEONEX, trade name, produced by Nippon Zeon Co., Ltd.)), and the like. Of these, triacetyl cellulose, polyethylene terephthalate, and polymers having an alicyclic structure are preferable, and triacetyl cellulose is particularly preferable.

  As will be described later, the angle formed by the slow axis direction of the λ / 4 plate and the absorption axis direction of the polarizing plate is 30 to 60 °, preferably 35 to 55 °, and preferably 40 to 50 °. Is more preferable, and 45 ° is particularly preferable. When the polarizing plate is produced by roll-to-roll, since the longitudinal direction (conveying direction) is usually the absorption axis direction, the angle formed between the slow axis direction of the λ / 4 plate and the longitudinal direction is 30 to 60 °. Preferably there is. As a method for producing a λ / 4 plate whose angle between the slow axis direction and the longitudinal direction is 30 to 60 °, the polymer orientation axis is obtained by continuously stretching in the direction of 30 to 60 ° with respect to the longitudinal direction. Any known method can be adopted as long as it is inclined to a desired angle. Further, the stretching machine used for the oblique stretching is not particularly limited, and a conventionally known tenter stretching machine that can add feed force, pulling force, or take-up force at different speeds in the horizontal or vertical direction can be used. . In addition, the tenter type stretching machine includes a horizontal uniaxial stretching machine, a simultaneous biaxial stretching machine, and the like, but is not particularly limited as long as a long film can be continuously obliquely stretched. These types of stretching machines can be used.

  Examples of the oblique stretching method include, for example, JP-A-50-83482, JP-A-2-113920, JP-A-3-182701, JP-A-2000-9912, JP-A-2002-86554, The methods described in JP-A-2002-22944 and International Publication No. 2007/111313 can be used.

  When the λ / 4 plate has an optically anisotropic layer or the like on a support made of a polymer film, another layer is laminated on the support to give a desired λ / 4 function. The constituent material of the optically anisotropic layer is not particularly limited, and may be a polymer formed from a composition containing a liquid crystal compound and exhibiting optical anisotropy expressed by molecular orientation of the liquid crystal compound. It may be a layer having optical anisotropy expressed by stretching a film and orienting a polymer in the film, or may have both layers. That is, it can be constituted by one or two or more biaxial films, or can be constituted by combining two or more uniaxial films such as a combination of a C plate and an A plate. Of course, it can also be configured by combining one or more biaxial films and one or more uniaxial films.

The λ / 4 plate preferably includes at least one layer formed from a composition containing a liquid crystal compound. That is, the λ / 4 plate is preferably a laminate of a polymer film (support) and an optically anisotropic layer formed from a composition containing a liquid crystal compound.
For the support, a polymer film having a small optical anisotropy may be used, or a polymer film exhibiting an optical anisotropy by a stretching process or the like may be used. The support preferably has a light transmittance of 80% or more. Specific examples of the support will be described later.

Further, the type of liquid crystal compound used for forming the optically anisotropic layer is not particularly limited. For example, an optically anisotropic layer obtained by forming a low-molecular liquid crystal compound in a nematic or smectic orientation in a liquid crystal state and then fixing by photocrosslinking or thermal crosslinking, or a nematic or smectic orientation in a liquid crystal state of a polymer liquid crystal compound After forming, an optically anisotropic layer obtained by fixing the orientation by cooling can also be used. In the present invention, even when a liquid crystal compound is used for the optically anisotropic layer, the optically anisotropic layer is a layer formed by fixing the liquid crystal compound by polymerization or the like, and thus becomes a layer. After that, it is no longer necessary to show liquid crystallinity. The polymerizable liquid crystal compound may be a polyfunctional polymerizable liquid crystal or a monofunctional polymerizable liquid crystal compound. The liquid crystal compound may be a discotic liquid crystal compound or a rod-shaped liquid crystal compound. In the present invention, a discotic liquid crystal compound is more preferable.
As a material and a production method for producing a λ / 4 plate formed from a composition containing a liquid crystal compound, the production of a light reflecting layer described later can be referred to. However, the composition for producing the λ / 4 plate preferably does not contain a chiral agent.

  In the optically anisotropic layer described above, the molecules of the liquid crystal compound are preferably fixed in any alignment state of vertical alignment, horizontal alignment, hybrid alignment, and tilt alignment. In order to produce a retardation plate having a symmetric viewing angle dependency, the disk surface of the disk-like liquid crystal compound is substantially perpendicular to the film surface (optically anisotropic layer surface), or a rod-like liquid crystal It is preferable that the long axis of the compound is substantially horizontal with respect to the film surface (optically anisotropic layer surface). The term “substantially perpendicular to the discotic liquid crystal compound” means that the average value of the angle formed by the film surface (optically anisotropic layer surface) and the disc surface of the discotic liquid crystal compound is in the range of 70 ° to 90 °. To do. 80 ° to 90 ° is more preferable, and 85 ° to 90 ° is still more preferable. That the rod-like liquid crystal compound is substantially horizontal means that the angle formed by the film surface (optically anisotropic layer surface) and the director of the rod-like liquid crystal compound is in the range of 0 ° to 20 °. 0 ° to 10 ° is more preferable, and 0 ° to 5 ° is still more preferable.

  The optically anisotropic layer described above comprises a coating liquid containing a liquid crystal compound such as a rod-like liquid crystal compound or a disk-like liquid crystal compound, and, if desired, a polymerization initiator, an alignment control agent and other additives, which are described later, on a support. It can be formed by coating. It is preferable to form an alignment layer on the support and apply the above-described coating solution to the surface of the alignment layer.

<Reflective polarizer>
In the brightness enhancement film, the reflective polarizer includes at least one light reflecting layer formed by fixing a cholesteric liquid crystal phase. It is also preferable that the reflective polarizer includes two or more light reflecting layers, and the reflective polarizer preferably includes 2 to 4 light reflecting layers, and more preferably includes 2 to 3 layers. It is preferable to include two layers.
In this specification, when two or more light reflecting layers of the reflective polarizer are referred to, the light reflecting layer closest to the λ / 4 plate side is referred to as the first light reflecting layer, and the light reflecting layer is in order from the λ / 4 plate side. The first light reflection layer, the second light reflection layer, the third light reflection layer, and the like are called.
In the brightness enhancement film, the reflective polarizer preferably has a function of reflecting blue light, green light, and red light. The reflective polarizer preferably includes a light reflecting layer that reflects blue light, green light, and red light, respectively, or at least one broadband light reflecting layer. In the present invention, the broadband light reflecting layer is a layer that reflects at least one color light of blue light, green light, and red light, and also reflects light in a wavelength region that exceeds the wavelength region of this one color. That means. For example, a layer that reflects blue light and green light in one layer, a layer that reflects green light and red light in one layer, or a layer that reflects blue light, green light, and red light in one layer may be used. .

Furthermore, as means for improving the oblique color change, a reflective polarizer configured so that the Rth of the light reflection layer included in two or more layers is reversed, or a reflection polarizer whose reflection band is extended to the infrared light region Is also preferable.
The principle of improving the color tone by extending the reflection band to the infrared region is shown below.
Even if the reflection band of the cholesteric liquid crystal layer covers red, green, and blue with respect to the front incident light, the reflection band shifts to the short-wave side for oblique light, so the red reflection layer is green for oblique light. For reflection, the green reflection layer becomes blue reflection, and the blue reflection layer becomes ultraviolet reflection.
Therefore, since the front is reflected with a good balance of red, green and blue, the color change is small, but in the diagonal direction, the red reflection component is reduced, the balance of red, green and blue is lost and the color change is worsened.
In order to prevent this, if a layer capable of reflecting the infrared region is inserted in the front, the infrared reflecting layer reflects red against oblique light, so that the balance of red, green and blue is maintained even in the oblique direction, and the color changes. Can be improved.

An example of a reflective polarizer which is one of the first preferred embodiments of the reflective polarizer and has two light reflective layers will be described below.
A light reflecting layer that reflects blue light and green light having a reflectance peak in which any one of the first light reflecting layer and the second light reflecting layer has a reflection center wavelength of 380 to 599 nm and a half width of 220 nm or less. It is preferable that any one of them is a red light reflecting layer having a reflectance peak having a reflection center wavelength of 600 to 750 nm and a half width of 200 nm or less.

The light reflection layer that reflects blue light and green light has a reflection peak having a reflection center wavelength in a wavelength band of 380 to 599 nm and a half width of 220 nm or less.
The reflection center wavelength of the light reflection layer that reflects blue light and green light is preferably in the wavelength band of 430 to 590 nm, and more preferably in the wavelength band of 430 to 580 nm.
The half-value width of the reflectance peak of the light reflecting layer that reflects blue light and green light is preferably 300 nm or less, more preferably the half-value width of this reflectance peak is 250 nm or less. The half width of the peak is more preferably 220 nm or less, the half width of the reflectance peak is particularly preferably 210 nm or less, and the half width of the reflectance peak is most preferably 200 nm or less.
The light reflecting layer that reflects blue light and green light preferably has no reflectance peak in the wavelength band of 600 to 750 nm. Moreover, it is preferable that the light reflection layer which reflects blue and green has an average reflectance of 600 to 750 nm of 5% or less.
The reflective layer that reflects blue light and green light preferably has a thickness d of 0.5 to 10 μm, and more preferably 1.0 μm or more and less than 9 μm.

The red light reflection layer has a reflection peak having a reflection center wavelength in a wavelength band of 600 to 750 nm and a half width of 200 nm or less.
The reflection center wavelength of the red light reflection layer is preferably in the wavelength band of 610 to 690 nm, and more preferably in the wavelength band of 610 to 660 nm.
The half width of the reflectance peak of the red light reflection layer is preferably 200 nm or less, the half width of the reflectance peak is more preferably 190 nm or less, and the half width of the reflectance peak is 180 nm or less. It is particularly preferred that
The red light reflection layer preferably does not have a reflectance peak in the wavelength bands of 380 to 499 nm and 500 to 599 nm. The red light reflecting layer preferably has an average reflectance of 380 to 499 nm and 500 to 599 nm of 5% or less.

An example of a reflective polarizer which is another one of the first preferred embodiments of the reflective polarizer and has two light reflective layers will be described below.
Among the first light reflection layer and the second light reflection layer of the reflective polarizer, any one is a blue light reflection layer having a reflectance peak with a reflection center wavelength of 380 to 499 nm and a half-value width of 120 nm or less, Any one of them is a light reflection layer that reflects green light and red light having a reflectance peak having a reflection center wavelength of 500 to 750 nm and a half width of 300 nm or less.

The blue light reflection layer has a reflection peak having a reflection center wavelength in a wavelength band of 380 to 499 nm and a half width of 120 nm or less.
The reflection center wavelength of the blue light reflection layer is preferably in the wavelength band of 430 to 480 nm, and more preferably in the wavelength band of 430 to 470 nm.
The full width at half maximum of the reflectance peak of the blue light reflecting layer is preferably 120 nm or less, more preferably the half width of this reflectance peak is 110 nm or less, and the half width of this reflectance peak is 100 nm or less. It is particularly preferred that
The blue light reflection layer preferably does not have a reflectance peak in the wavelength band of 500 to 750 nm. The blue light reflection layer preferably has an average reflectance of 500 to 750 nm of 5% or less.
The blue light reflecting layer preferably has a film thickness d of 0.5 to 3.0 μm, and more preferably 1.0 to 2.6 μm.

The light reflection layer that reflects green light and red light has a reflection center wavelength in a wavelength band of 500 to 750 nm, and has a reflectance peak with a half width of 300 nm or less.
The reflection center wavelength of the light reflection layer that reflects green light and red light is preferably in the wavelength band of 520 to 690 nm, and more preferably in the wavelength band of 520 to 660 nm.
The half value width of the reflectance peak of the light reflecting layer that reflects green light and red light is preferably 300 nm or less, more preferably the half value width of the reflectance peak is 290 nm or less. It is particularly preferable that the half width of the peak is 280 nm or less.
The light reflection layer that reflects green light and red light preferably has no reflectance peak in the wavelength band of 380 to 499 nm. Moreover, it is preferable that the light reflection layer which reflects green light and red light has an average reflectance of 380 to 499 nm of 5% or less.
The light reflection layer that reflects green light and red light preferably has a film thickness d of 0.8 to 10 μm, and more preferably 1.5 μm or more and less than 9 μm.

An example of a reflective polarizer that is still another one of the first preferred embodiments of the reflective polarizer and has three light reflective layers will be described below.
A blue light reflection layer having a reflectance peak in which any one of the first light reflection layer, the second light reflection layer, and the third light reflection layer has a reflection center wavelength of 380 to 499 nm and a half width of 100 nm or less. Any one is a green light reflecting layer having a reflectance peak having a reflection center wavelength of 500 to 599 nm and a half-value width of 200 nm or less, and any one of them has a reflection center wavelength of 600 to 750 nm and a half-value width of 150 nm or less. A reflective polarizer, which is a red light reflective layer having a reflectance peak, wherein the sign of Rth (550) of the first light reflective layer is opposite to the sign of Rth (550) of the second light reflective layer. It is.

<Light reflection layer>
The light reflection layer formed by fixing the cholesteric liquid crystal phase exhibits selective reflection having a reflection center wavelength λ based on the helical period of the cholesteric liquid crystal phase. The light reflection layer formed by fixing the cholesteric liquid crystal phase selectively reflects either the right circularly polarized light or the left circularly polarized light and transmits the other circularly polarized light in the wavelength region exhibiting selective reflection. The reflection center wavelength λ depends on the pitch P (helical period) of the helical structure in the cholesteric liquid crystal phase, and follows the relationship between the average refractive index n of the cholesteric liquid crystal layer and λ = n × P. The average refractive index n is (no + ne) / 2 described above. The half-value width Δλ of selective reflection depends on the relationship of Δλ = Δn × P, where Δλ depends on the birefringence Δn of the liquid crystal compound and the pitch P.
(Polymerizable liquid crystal composition)
The polymerizable liquid crystal composition for forming the light reflecting layer contains a liquid crystal compound. The polymerizable liquid crystal composition for forming the light reflecting layer includes a chiral agent, an alignment controller, a polymerization initiator, an alignment aid, and the like. Other components may be contained.
The light reflection layer can be obtained by applying the polymerizable liquid crystal composition to another layer such as a λ / 4 plate, another light reflection layer, a temporary support, or an alignment layer, and then curing the coating film.

(Liquid crystal compound)
Examples of the liquid crystal compound include a rod-like liquid crystal compound and a disk-like liquid crystal compound.
Examples of the rod-like liquid crystal compound include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. In addition to the above low-molecular liquid crystalline molecules, high-molecular liquid crystalline molecules can also be used.

  It is more preferable to fix the orientation of the rod-like liquid crystal compound by polymerization, and examples of the polymerizable rod-like liquid crystal compound include those described in Makromol. Chem. 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. Nos. 4,683,327, 5,622,648 and 5,770,107, WO 95/22586, 95/24455. Publication No. 97/00600, No. 98/23580, No. 98/52905, JP-A-1-272551, No. 6-16616, No. 7-110469, No. 11-80081 The compounds described in JP-A-2001-328773 and the like can be used. Further, as the rod-like liquid crystal compound, for example, those described in JP-T-11-513019 and JP-A-2007-279688 can be preferably used.

As the discotic liquid crystal compound, for example, those described in JP-A-2007-108732 and JP-A-2010-244038 can be preferably used, but are not limited thereto.
Although the preferable example of a disk shaped liquid crystal compound is shown below, this invention is not limited to these.

  When the reflective polarizer includes two or more light reflecting layers, any one or more of the light reflecting layers is a layer formed from a polymerizable liquid crystal composition containing a rod-like liquid crystal compound, and any one of the other A layer formed from a polymerizable liquid crystal composition containing a discotic liquid crystal compound is preferred. The rod-like liquid crystal compound substantially acts as a positive Rth for light having a wavelength other than the wavelength range exhibiting selective reflection, and the discotic liquid crystal compound acts as a negative Rth substantially. By reversing the sign of Rth of two light reflecting layers among a plurality of light reflecting layers, it is possible to compensate for the phase difference and improve the oblique color change. Such two light reflection layers are preferably a first light reflection layer and a second light reflection layer. By adopting a configuration using the rod-like liquid crystal compound and the disk-like liquid crystal compound, the phase difference can be compensated and the oblique color change can be improved.

(Chiral agent)
A chiral agent is a compound for adjusting the helical period of a cholesteric liquid crystalline compound, and is also called a chiral agent. In the present invention, various known chiral agents (for example, liquid crystal device handbook, Chapter 3-4-3, TN, chiral agent for STN, 199 pages, edited by Japan Society for the Promotion of Science, 42nd Committee, 1989) ) Can be used. A chiral agent generally contains an asymmetric carbon atom, but an axially asymmetric compound or a planar asymmetric compound containing no asymmetric carbon atom can also be used as the chiral agent. Examples of the axial asymmetric compound or the planar asymmetric compound include binaphthyl, helicene, paracyclophane, and derivatives thereof. The chiral agent may have a polymerizable group. When the chiral agent has a polymerizable group and the rod-shaped liquid crystal compound used in combination also has a polymerizable group, it is derived from the rod-shaped liquid crystal compound by a polymerization reaction between the chiral agent having a polymerizable group and the polymerizable rod-shaped liquid crystal compound. And a polymer having a repeating unit derived from a chiral agent. In this embodiment, the polymerizable group possessed by the chiral agent having a polymerizable group is preferably the same group as the polymerizable group possessed by the polymerizable rod-like liquid crystal compound. Therefore, the polymerizable group of the chiral agent is also preferably an unsaturated polymerizable group, an epoxy group or an aziridinyl group, more preferably an unsaturated polymerizable group, and an ethylenically unsaturated polymerizable group. Particularly preferred.

Further, the above chiral agent may be a liquid crystal compound.
Examples of the chiral agent exhibiting a strong twisting force include JP 2010-181852 A, JP 2003-287623 A, JP 2002-80851 A, JP 2002-80478 A, and JP 2002-302487 A. The chiral agent etc. which are described in gazette are mentioned, It can use preferably for this invention. Furthermore, isosorbide compounds having a corresponding structure can be used for the isosorbide compounds described in these publications, and isosorbide compounds having a corresponding structure can be used for the isomannide compounds described in these publications. It can also be used.

(Orientation control agent)
Examples of the alignment control agent include compounds exemplified in [0092] and [0093] of JP-A-2005-99248, and [0076] to [0078] and [0082] of JP-A-2002-129162. To [0085], the compounds exemplified in JP-A-2005-99248, [0094] and [0095], and JP-A-2005-99248, [0096]. Are included.
As the alignment control agent, compounds described in [0082] to [0090] of JP-A No. 2014-119605 can also be used.

(Polymerization initiator)
Examples of the polymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatics. An acyloin compound (described in US Pat. No. 2,722,512), a polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of a triarylimidazole dimer and p-aminophenyl ketone (US Pat. 3549367), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850) and oxadiazole compounds (US Pat. No. 4,221,970), acylphosphine oxides Compound (Japanese Examined Patent Publication Sho 63-407) No. 99, JP-B-5-29234, JP-A-10-95788, JP-A-10-29997) and the like.

(solvent)
The polymerizable liquid crystal composition may contain a solvent. As a solvent of the composition for forming each light reflection layer, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone, cyclohexanone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.

(Application and curing of polymerizable liquid crystal composition)
The application of the polymerizable liquid crystal composition is carried out by using a suitable liquid crystal composition such as a roll coating method, a gravure printing method, a spin coating method, etc. It can be performed by a method of developing by a method. Furthermore, it can be performed by various methods such as a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, and a die coating method. In addition, a coating film can be formed by discharging a liquid crystal composition from a nozzle using an inkjet apparatus.
Thereafter, the polymerizable liquid crystal composition is cured to fix the alignment state of the molecules of the liquid crystal compound. Curing is preferably carried out by a polymerization reaction of a polymerizable group introduced into a liquid crystal molecule.
The coating film may be dried by a known method after the application of the polymerizable liquid crystal composition and before the polymerization reaction for curing. For example, it may be dried by standing or may be dried by heating.
The liquid crystal compound molecules in the polymerizable liquid crystal composition only need to be aligned in the steps of applying and drying the polymerizable liquid crystal composition.

  For example, in an embodiment in which the polymerizable liquid crystal composition is prepared as a coating solution containing a solvent, the coating film may be dried and the solvent may be removed to obtain a cholesteric liquid crystal phase. Further, heating at a transition temperature to the cholesteric liquid crystal phase may be performed. For example, the cholesteric liquid crystal phase can be stably formed by heating to the temperature of the isotropic phase and then cooling to the cholesteric liquid crystal phase transition temperature. The liquid crystal phase transition temperature of the above-described polymerizable liquid crystal composition is preferably in the range of 10 to 250 ° C., more preferably in the range of 10 to 150 ° C. from the viewpoint of production suitability and the like. When the temperature is lower than 10 ° C., a cooling step or the like may be required to lower the temperature to a temperature range exhibiting a liquid crystal phase. When the temperature exceeds 200 ° C., a high temperature is required to make the isotropic liquid state higher than the temperature range once exhibiting the liquid crystal phase, which is disadvantageous from waste of thermal energy, deformation of the substrate, and alteration.

The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred. It is preferable to use ultraviolet rays for light irradiation for polymerization of liquid crystalline molecules. The irradiation energy is preferably ^{20mJ / cm 2 ~50J / cm 2} , further preferably 100 to 800 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.

In order to accelerate the curing reaction, ultraviolet irradiation may be performed under heating conditions. In particular, when forming the light reflecting layer, it is preferable to maintain the temperature at the time of ultraviolet irradiation within a temperature range exhibiting a cholesteric liquid crystal phase so that the cholesteric liquid crystal phase is not disturbed.
Also, since the oxygen concentration in the atmosphere is related to the degree of polymerization, if the desired degree of polymerization is not reached in the air and the film strength is insufficient, the oxygen concentration in the atmosphere is reduced by a method such as nitrogen substitution. It is preferable. A preferable oxygen concentration is preferably 10% or less, more preferably 7% or less, and most preferably 3% or less. The reaction rate of the curing reaction (for example, polymerization reaction) that proceeds by irradiation with ultraviolet rays is 70% or more from the viewpoint of maintaining the mechanical strength of the layer and suppressing unreacted substances from flowing out of the layer. Preferably, it is 80% or more, more preferably 90% or more. In order to improve the reaction rate, a method of increasing the irradiation amount of ultraviolet rays to be irradiated and polymerization under a nitrogen atmosphere or heating conditions are effective. Moreover, after superposing | polymerizing once, the method of hold | maintaining at a temperature higher than superposition | polymerization temperature, and pushing a reaction further by thermal polymerization reaction, and the method of irradiating an ultraviolet-ray again can also be used. The reaction rate can be measured by comparing the absorption intensity of the infrared vibration spectrum of a reactive group (for example, a polymerizable group) before and after the reaction proceeds.

  It is sufficient that the optical properties based on the orientation of the liquid crystal compound molecules of the polymerizable liquid crystal composition, for example, the optical properties of the cholesteric liquid crystal phase are retained in the layer, and the cured λ / 4 plate or light reflection The liquid crystal composition of the layer no longer needs to exhibit liquid crystallinity. For example, the liquid crystal composition may have a high molecular weight due to a curing reaction and may no longer have liquid crystallinity.

In the formation of the light reflection layer, the cholesteric liquid crystal phase is fixed by the above-described curing, and the light reflection layer is formed. Here, the state in which the liquid crystal phase is “fixed” is the most typical and preferred mode in which the orientation of the liquid crystal compound in the cholesteric liquid crystal phase is maintained. However, it is not limited to this. Specifically, this layer usually has no fluidity in the temperature range of 0 ° C. to 50 ° C., and -30 ° C. to 70 ° C. under more severe conditions, and is oriented by an external field or external force. It shall mean a state in which the fixed orientation form can be kept stable without causing a change in form.
Other methods for producing a light reflecting layer in which a cholesteric liquid crystal phase is fixed include, for example, the methods described in JP-A-1-133003, JP-A-3416302, JP-A-3363565, and JP-A-8-271731. You may refer to it.

<Alignment layer>
The brightness enhancement film may include an alignment layer. The alignment layer is used to align the molecules of the liquid crystal compound in the polymerizable composition when the λ / 4 plate or the light reflection layer is formed.
The alignment layer is used in the formation of the λ / 4 plate or the light reflection layer, and the brightness enhancement film may or may not include the alignment layer.

The alignment layer can be provided by means such as a rubbing treatment of an organic compound (preferably a polymer), oblique vapor deposition of an inorganic compound such as SiO, or formation of a layer having microgrooves. Furthermore, an alignment layer in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known.
Depending on the underlying material such as the support, the λ / 4 plate, or the light reflection layer, the support may be functioned as an alignment layer by direct alignment treatment (for example, rubbing treatment) without providing an alignment layer. it can. An example of such a lower layer support is PET.
Further, when the light reflecting layer is laminated directly on the light reflecting layer, the lower light reflecting layer may behave as an alignment layer, and the liquid crystal compound for producing the upper light reflecting layer may be aligned. In such a case, the upper liquid crystal compound can be aligned without providing an alignment layer or without performing a special alignment process (for example, rubbing process).
Hereinafter, a rubbing-treated alignment layer and a photo-alignment layer used by rubbing the surface as preferred examples will be described.

(Rubbing alignment layer)
Examples of the polymer that can be used for the rubbing treatment oriented layer include, for example, a methacrylate copolymer, a styrene copolymer, a polyolefin, polyvinyl alcohol, and the like described in paragraph No. [0022] of JP-A-8-338913. Examples include modified polyvinyl alcohol, poly (N-methylolacrylamide), polyester, polyimide, vinyl acetate copolymer, carboxymethylcellulose, and polycarbonate. Silane coupling agents can be used as the polymer. Water-soluble polymers (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol) are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol are most preferred. .

The aforementioned composition is applied to the rubbing-treated surface of the alignment layer to align the molecules of the liquid crystal compound. After that, if necessary, the alignment layer polymer and the polyfunctional monomer contained in the optically anisotropic layer are reacted, or the alignment layer polymer is crosslinked using a crosslinking agent, thereby the optical anisotropy described above. A layer can be formed.
The thickness of the alignment layer is preferably in the range of 0.1 to 10 μm.

-Rubbing treatment-
The surface of the alignment layer, temporary support, λ / 4 plate, or light reflection layer to which the polymerizable liquid crystal composition is applied may be rubbed as necessary. The rubbing treatment can be generally performed by rubbing the surface of a film containing a polymer as a main component with paper or cloth in a certain direction. A general method of rubbing is described in, for example, “Liquid Crystal Handbook” (issued by Maruzen, October 30, 2000).

As a method for changing the rubbing density, a method described in “Liquid Crystal Handbook” (published by Maruzen) can be used. The rubbing density (L) is quantified by the following formula (A).
Formula (A) L = Nl (1 + 2πrn / 60v)
In the formula (A), N is the number of rubbing, l is the contact length of the rubbing roller, r is the radius of the roller, n is the number of rotations (rpm) of the roller, and v is the stage moving speed (second speed).

  In order to increase the rubbing density, the rubbing frequency should be increased, the contact length of the rubbing roller should be increased, the radius of the roller should be increased, the rotation speed of the roller should be increased, and the stage moving speed should be decreased, while the rubbing density should be decreased. To do this, you can reverse this. In addition, the description in Japanese Patent No. 4052558 can also be referred to as conditions for the rubbing process.

(Photo-alignment layer)
A large number of documents describe the photo-alignment material used for the photo-alignment layer formed by light irradiation. For example, JP 2006-285197 A, JP 2007-76839 A, JP 2007-138138 A, JP 2007-94071 A, JP 2007-121721 A, JP 2007-140465 A, Azo compounds described in JP 2007-156439 A, JP 2007-133184 A, JP 2009-109831 A, Patent 3888848, Patent 4151746, and Fragrance described in JP 2002-229039 A. Group ester compounds, maleimide and / or alkenyl-substituted nadiimide compounds having a photo-alignment unit described in JP-A No. 2002-265541 and JP-A No. 2002-317013, light described in Japanese Patent No. 4205195 and Japanese Patent No. 4205198 Crosslinkable silane derivative, special 2003-520878, JP-T-2004-529220 and JP-mentioned as photocrosslinkable polyimide, polyamide or ester are preferable examples described in Japanese Patent No. 4162850. Particularly preferred are azo compounds, photocrosslinkable polyimides, polyamides, or esters.

The photo-alignment layer formed from the above material is irradiated with linearly polarized light or non-polarized light to produce a photo-alignment layer.
In this specification, “linearly polarized light irradiation” is an operation for causing a photoreaction in a photo-alignment material. The wavelength of light used varies depending on the photo-alignment material used, and is not particularly limited as long as it is a wavelength necessary for the photoreaction. Preferably, the peak wavelength of light used for light irradiation is 200 nm to 700 nm, more preferably ultraviolet light having a peak wavelength of light of 400 nm or less.

  The light source used for light irradiation is a commonly used light source such as a tungsten lamp, a halogen lamp, a xenon lamp, a xenon flash lamp, a mercury lamp, a mercury xenon lamp, a carbon arc lamp, or various lasers (eg, semiconductor laser, helium). Neon laser, argon ion laser, helium cadmium laser, YAG laser), light emitting diode, cathode ray tube, and the like.

  As means for obtaining linearly polarized light, a method using a polarizing plate (eg, iodine polarizing plate, dichroic dye polarizing plate, wire grid polarizing plate), reflection using a prism-based element (eg, Glan-Thompson prism) or Brewster angle A method using a type polarizer or a method using light emitted from a laser light source having polarization can be employed. Moreover, you may selectively irradiate only the light of the required wavelength using a filter, a wavelength conversion element, etc.

In the case of linearly polarized light, a method of irradiating light from the top surface or the back surface to the alignment layer surface perpendicularly or obliquely with respect to the alignment layer is employed. Although the incident angle of light changes with photo-alignment materials, it is 0-90 degrees (vertical), for example, Preferably it is 40-90.
When non-polarized light is used, the non-polarized light is irradiated obliquely. The incident angle is 10 to 80 °, preferably 20 to 60, and particularly preferably 30 to 50 °.
The irradiation time is preferably 1 minute to 60 minutes, more preferably 1 minute to 10 minutes.

<Preparation of broadband light reflection layer>
Examples of a method for broadening the light reflection layer formed by fixing the cholesteric liquid crystal phase include use of a high Δn liquid crystal compound and a pitch gradient method.
Δn is the birefringence of the liquid crystal compound as described above. For example, in the case of a rod-like liquid crystal compound, it is the difference in refractive index between the minor axis and the major axis of the compound.
The liquid crystal compound used in the light reflecting layer formed by fixing the cholesteric liquid crystal phase is practically about 0.06 ≦ Δn ≦ 0.5 (the high Δn liquid crystal material described in JP 2011-510915 A can be used). Yes, corresponding to 15 to 150 nm in half width. Further, examples of the high Δn liquid crystal compound include compounds described in Japanese Patent No. 3999400, Japanese Patent No. 4053782, Japanese Patent No. 4947676, and the like, but are not limited thereto. The method of paragraph [0112] of Japanese Patent No. 40537882 and paragraph [0142] of Japanese Patent No. 4947676 can be referred to for the method of measuring Δn.
When manufacturing by controlling the half-value width of 200 nm or less, a pitch gradient method that can realize a wide half-value width can be used by gradually changing the number of pitches in the cholesteric spiral direction instead of a single pitch. The pitch is the pitch length P of the helical structure in the cholesteric liquid crystal phase, and means the thickness of the molecular layer when the orientation direction of the molecular layer of the liquid crystal compound is rotated 360 degrees.

From the viewpoints of half-width expansion and film thickness reduction (thinning) with a pitch gradient, Δn is preferably 0.16 or more, more preferably 0.2 or more, still more preferably 0.3 or more, and particularly preferably the present situation. It is about 0.5 which is the upper limit of Δn of the liquid crystal that has been industrialized. However, if further high Δn liquid crystal is developed in the future, it can be applied to the present invention in principle and can be made thinner.
In the case of using a liquid crystal compound having Δn of 0.156 from the viewpoint of luminance performance, and having at least a pitch gradient band of 400 to 600 nm, the film thickness of the wideband pitch gradient layer is preferably 6 μm or more, and 8 μm or more. More preferably, 10 μm or more is even more preferable. In the case of using a liquid crystal compound having Δn of 0.3 and having at least a pitch gradient band of 400 to 600 nm, the film thickness is preferably 2 μm or more, more preferably 3 μm or more, further preferably 4 μm or more, and 5 μm or more. Is particularly preferred.

  It is known that it is preferable that the Δn dispersion of the liquid crystal has a small dispersion at each wavelength. Preferably Δn (450/550 ratio) ≦ 1.6, more preferably Δn (450/550 ratio) ≦ 1.4, more preferably Δn (450/550 ratio) ≦ 1.2, particularly preferably Δn. (450/550 ratio) ≦ 1.1.

In the pitch gradient method, a wide half-value width can be realized by gradually changing the pitch in the spiral direction (normal film thickness direction) of the cholesteric liquid crystal phase. In the light reflection layer to which the pitch gradient method is applied, it is preferable that the pitch continuously changes in the film thickness direction. Moreover, in the light reflection layer to which the pitch gradient method is applied, it is preferable that the pitch continuously increases or decreases continuously from one surface of the layer to the other surface. In the pitch gradient method, the concentration of a compound that does not form a spiral in the thickness direction of the liquid crystal layer is continuously changed in the thickness direction of the liquid crystal layer, or the concentration of the chiral agent is continuously changed in the thickness direction of the liquid crystal layer. Alternatively, use a chiral agent with a photoisomerization moiety, and change the HTP (helical twisting power) of the chiral agent by isomerizing the photoisomerization part of the chiral agent with UV irradiation etc. when forming the light reflection layer. To achieve this. As this photoisomerization moiety, a vinylene group, an azo group, or the like is preferable.
As the pitch gradient method, those described in (Nature 378, 467-469 1995), Japanese Patent No. 4990426, Japanese Patent Application Laid-Open No. 2005-265896, and the like can be applied. Moreover, the compound which does not form a helix and has a fluorinated alkyl group as described in Japanese Patent No. 4570377 can also be used.

<Phase difference element>
The brightness enhancement film may have a retardation element, for example, to compensate for the phase difference of light incident obliquely on the ¼ plate from the backlight unit side. The retardation element has Rth in the range of −20 nm to −1000 nm, preferably −50 nm to −500 nm. Regarding the retardation element, the description in paragraphs 0045 to 0051 of Japanese Patent No. 4570377 can be referred to.

<Support>
The brightness enhancement film may include a support. A support body can function as a layer which supports the layer formed from the composition containing a liquid crystal compound.
In the brightness enhancement film, the light reflection layer may be formed using the λ / 4 plate itself as a support, or the light reflection layer may be formed using the entire λ / 4 plate formed on the support as a support. It may be formed.
The brightness enhancement film may not include a support for forming the light reflecting layer. For example, the light reflecting layer is formed by using glass or a transparent film as a support for forming the light reflecting layer. After that, only the light reflection layer may be peeled off from the support during film formation to form a brightness enhancement film. In the present specification, the support that is peeled off from the light reflecting layer in this way may be referred to as a temporary support. When only the first and second light reflecting layers are peeled off from the temporary support after the first and second light reflecting layers are formed, the λ / 4 plate and the adhesive layer (and / or the adhesive material) It is preferable to use the laminated | multilayer film, and it is set as a brightness improvement film by bonding the 1st and 2nd light reflection layer which peels with an contact bonding layer.
In addition, a film in which a λ / 4 plate and a first light reflection layer are formed in this order on a support, and a film in which a second light reflection layer is formed on a support, these first light reflection layers are used. It is also preferable to provide a brightness enhancement film by providing and bonding an adhesive layer (and / or an adhesive material) between the first light reflecting layer and the second light reflecting layer. At this time, the support may or may not be peeled off after bonding. Similarly, a film in which a λ / 4 plate and a first light reflecting layer are formed in this order on a support and a film in which a third light reflecting layer and a second light reflecting layer are formed in this order on a support are used. It is also preferable to provide a brightness enhancement film by providing and bonding an adhesive layer (and / or an adhesive material) between the first light reflecting layer and the second light reflecting layer.

The Re of the support is preferably 0 to 50 nm, more preferably 0 to 30 nm, and more preferably 0 to 30 nm when the support does not have a function as a part or all of the λ / 4 plate. More preferably, it is 10 nm. The above range is preferable because light leakage of reflected light can be reduced to a level where it is not visually recognized.
The retardation (Rth) in the thickness direction of the support is preferably selected depending on the combination with the optically anisotropic layer provided above or below it. Thereby, it is possible to reduce the light leakage of the reflected light and the coloring when observed from an oblique direction. Rth of the support is, for example, preferably from -40 to 120 nm, more preferably from 0 to 80 nm, still more preferably from 20 to 60 nm.

  Examples of the material of the polymer film used as the support include materials used for the above-mentioned λ / 4 plate, cellulose acylate films (for example, cellulose triacetate film (refractive index 1.48), cellulose diacetate film, cellulose Acetate butyrate film, cellulose acetate propionate film), polyolefin such as polyethylene and polypropylene, polyester resin film such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone film, polyacrylic resin film such as polymethyl methacrylate, polyurethane Resin film, polyester film, polycarbonate film, polysulfone film, polyether film, polymethylpentene film, poly -Terketone film, (meth) acrylonitrile film, polyolefin, polymer having alicyclic structure (norbornene resin (Arton: trade name, manufactured by JSR Corporation), amorphous polyolefin (Zeonex: trade name, manufactured by Nippon Zeon) Among them, triacetyl cellulose, polyethylene terephthalate, and polymers having an alicyclic structure are preferable, and triacetyl cellulose is particularly preferable.

  The thickness of the transparent support may be about 5 μm to 150 μm, preferably 5 μm to 80 μm, and more preferably 20 μm to 60 μm. The transparent support may be composed of a plurality of laminated layers. A thinner one is preferable for suppressing external light reflection, but if it is thinner than 5 μm, the strength of the film tends to be low, which tends to be undesirable. In order to improve adhesion between the transparent support and the layer (adhesive layer, vertical alignment layer or retardation layer) provided thereon, surface treatment (eg, glow discharge treatment, corona discharge treatment, ultraviolet light (UV) ) Treatment, flame treatment). An adhesive layer (undercoat layer) may be provided on the transparent support. Moreover, the average particle diameter is 10 to 100 nm in order to provide the transparent support or the long transparent support with slipperiness in the conveying process or to prevent the back surface and the surface from sticking after winding. It is preferable to use what formed the polymer layer which mixed the inorganic particle of about 5%-40% by solid content mass ratio on the one side of the support body by application | coating or co-casting with a support body.

  When the support is a temporary support, a glass plate may be used, for example, Corning glass 7059 may be used. As the temporary support, any of the plastic films exemplified as the support can be used, but it is preferable that the light reflecting layer formed by fixing the cholesteric liquid crystal phase can be peeled off and transferred. As the temporary support, for example, a long cellulose acylate film (TD80UL (manufactured by FUJIFILM Corporation)) of 100 meters or more may be used. The use of a long cellulose acylate film in this manner enables the production of an optical sheet member by so-called roll-to-roll, and is more preferable from the viewpoint of manufacturing suitability. The long film to be used is not limited to this as long as the cholesteric liquid crystal layer can be transferred.

<Adhesive layer (adhesive layer), adhesive>
In this specification, “adhesion” is used in a concept including “adhesion”.
An adhesive layer may be included between each member constituting the brightness enhancement film and the optical sheet member described later. For example, an adhesive layer is included between the λ / 4 plate and the reflective polarizer, between the light reflecting layers in the reflective polarizer, between the polarizing plate or the polarizer and the λ / 4 plate, and the like. Also good.
As the pressure-sensitive adhesive used for the adhesive layer, for example, the ratio (tan δ = G ″ / G ′) of the storage elastic modulus G ′ and loss elastic modulus G ″ measured by a dynamic viscoelasticity measuring device is 0.001 to 1. .5, which includes so-called pressure-sensitive adhesives and substances that are easy to creep. Examples of the pressure-sensitive adhesive that can be used in the present invention include, but are not limited to, acrylic pressure-sensitive adhesives and polyvinyl alcohol-based adhesives.

  Examples of the adhesive include a boron compound aqueous solution, an epoxy compound curable adhesive that does not contain an aromatic ring in the molecule, as disclosed in JP-A-2004-245925, and 360 described in JP-A-2008-174667. An active energy ray-curable adhesive comprising a photopolymerization initiator having a molar extinction coefficient of 400 or more at a wavelength of ˜450 nm and an ultraviolet curable compound as essential components, (meth) acrylic as described in JP-A-2008-174667 (A) (meth) acrylic compound having 2 or more (meth) acryloyl groups in the molecule in 100 parts by mass of the total amount of the compound, and (b) having a hydroxyl group in the molecule, and only having a polymerizable double bond (Meth) acrylic compound having one and (c) phenol ethylene oxide modified acrylate or nonylphenol ethylene oxide The active energy ray-curable adhesive containing a sex acrylate, and the like.

The optical sheet member described later preferably has a refractive index difference of 0.15 or less, more preferably 0.10 or less, between the reflective polarizer and the layer adjacent to the polarizing plate side of the reflective polarizer. Is particularly preferably 0.05 or less. Examples of the layer adjacent to the polarizing plate side of the above-described reflective polarizer include the above-described adhesive layer.
The method for adjusting the refractive index of the adhesive layer is not particularly limited, but for example, a method described in JP-A-11-223712 can be used. Among the methods described in JP-A-11-223712, the following embodiments are particularly preferable.

  Examples of the pressure-sensitive adhesive used for the adhesive layer include resins such as polyester resins, epoxy resins, polyurethane resins, silicone resins, and acrylic resins. You may use these individually or in mixture of 2 or more types. In particular, an acrylic resin is preferable because it is excellent in reliability such as water resistance, heat resistance, and light resistance, has good adhesion and transparency, and can easily adjust the refractive index to be compatible with a liquid crystal display. As acrylic pressure-sensitive adhesive, acrylic acid and its esters, methacrylic acid and its esters, acrylamide, homopolymers of acrylic monomers such as acrylonitrile, or their copolymers, and at least one of the above acrylic monomers, Examples thereof include copolymers with aromatic vinyl monomers such as vinyl acetate, maleic anhydride, and styrene. In particular, main monomers such as ethylene acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc. that exhibit tackiness, monomers such as vinyl acetate, acrylonitrile, acrylamide, styrene, methacrylate, methyl acrylate as cohesive components, Functional group containing methacrylic acid, acrylic acid, itaconic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, acrylamide, methylol acrylamide, glycidyl methacrylate, maleic anhydride, etc. A copolymer composed of monomers, having a Tg (glass transition point) in the range of −60 ° C. to −15 ° C. and a weight average molecular weight in the range of 200,000 to 1,000,000. Shall is preferable.

  A sheet-like photo-curing adhesive (described in Toagosei Group Research Annual Report TREND No. 14 issued on January 1, 2011) can also be used for the adhesive layer. Like an adhesive, it is easy to bond between optical films, is crosslinked and cured with ultraviolet rays (UV), and improves storage elastic modulus, adhesive strength and heat resistance, which is preferable.

<Method for producing brightness enhancement film>
As a method for producing the brightness enhancement film, a separately produced λ / 4 plate and a light reflecting layer may be bonded together with an adhesive, and at least one light reflecting layer is placed on the surface of the λ / 4 plate or another light reflecting layer. It may be formed by direct application. By forming by direct coating, it is possible to provide a brightness enhancement film having better flexibility. It is also preferable that all the light reflection layers are formed by being directly applied to the surface of the λ / 4 plate or the other light reflection layer.

The method for producing the brightness enhancement film is, for example, by applying a polymerizable liquid crystal composition to the surface of a λ / 4 plate, which is a polymer film, and curing the coating film to form a light reflecting layer (first light reflecting layer). Including doing. A polymerizable liquid crystal composition is further applied to the surface of the laminate of the λ / 4 plate and the first light reflection layer produced as described above, the coating film is cured, and the light reflection layer (second light (Reflection layer) may be formed, and the coating film may be further cured to form a light reflection layer (third light reflection layer). Or you may laminate | stack the light reflection layer (2nd light reflection layer) formed on the support body (temporary support body) using the contact bonding layer. The temporary support may or may not be peeled off thereafter. The brightness enhancement film may be produced by a method including producing a λ / 4 plate by applying a composition containing a liquid crystal compound on a support and curing the coating film. A λ / 4 plate and a light reflection layer may be sequentially formed on the support by coating and curing. A laminate having a λ / 4 plate on the support, and a laminate having a light reflection layer on the temporary support, May be bonded so that the λ / 4 plate and the light reflecting layer are adjacent to each other. For example, a laminate having a λ / 4 plate on a support, and a laminate having a second light reflecting layer and a first light reflecting layer in this order from the temporary support on the temporary support, The four plates and the first light reflecting layer may be bonded so as to be adjacent to each other. Thereafter, the temporary support may or may not be peeled off.
When forming a λ / 4 plate formed of a composition containing a liquid crystal compound and a light reflecting layer in which a cholesteric liquid crystal phase is fixed, a method of superimposing a liquid crystal layer through an alignment layer can also be employed.

<Optical sheet member>
The optical sheet member has a brightness enhancement film and a polarizing plate. An example of the layer structure of the optical sheet member is shown in FIG. The angle formed by the slow axis of the λ / 4 plate and the absorption axis of the polarizer is 30 to 60 °, and the polarizing plate, the λ / 4 plate, and the reflective polarizer are in direct contact in this order, or an adhesive layer It is preferable to laminate via. The slow axis means a direction in which the refractive index is maximized.
The optical sheet member may have a polarizing plate protective film. When the polarizing plate protective film is not provided between the polarizer and the reflective polarizer, the reflective polarizer may be provided directly on the polarizer or via an adhesive. The λ / 4 plate may also serve as a polarizing plate protective film, and the polarizing plate protective film may also serve as a part of the λ / 4 plate realized by lamination.
Among these protective films, as the protective film disposed on the side opposite to the liquid crystal cell, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth) acrylic resins, cyclic Examples thereof include polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof.

<Polarizing plate>
Although a polarizing plate may consist only of a polarizer, it is preferable that a polarizing plate is comprised with the polarizing plate and the polarizing plate protective film which protects the at least single side | surface. It is also preferable to consist of a polarizer and two polarizing plate protective films (hereinafter also referred to as protective films) disposed on both sides thereof.

(Polarizer)
As the polarizer, it is preferable to use a polymer film in which iodine is adsorbed and oriented. The polymer film is not particularly limited, and various types can be used. For example, polyvinyl alcohol films, polyethylene terephthalate films, ethylene / vinyl acetate copolymer films, partially saponified films of these, hydrophilic polymer films such as cellulose films, polyvinyl alcohol dehydrated products and polychlorinated Examples include polyene-based oriented films such as vinyl dehydrochlorinated products. Among these, it is preferable to use a polyvinyl alcohol film excellent in dyeability with iodine as a polarizer.

  Polyvinyl alcohol or a derivative thereof is used as the material for the polyvinyl alcohol film. Derivatives of polyvinyl alcohol include polyvinyl formal, polyvinyl acetal and the like, olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, alkyl esters thereof, acrylamide and the like. Can be mentioned.

  The degree of polymerization of the polymer that is the material of the polymer film is generally 500 to 10,000, preferably in the range of 1000 to 6000, and more preferably in the range of 1400 to 4000. Furthermore, in the case of a saponified film, the saponification degree is preferably 75 mol% or more, more preferably 98 mol% or more, for example, from the viewpoint of solubility in water, and 98.3 to 99.8 mol. % Is more preferable.

The aforementioned polymer film (unstretched film) is at least subjected to uniaxial stretching treatment and iodine dyeing treatment according to a conventional method. Furthermore, a boric acid treatment or a washing treatment can be performed. Further, the polymer film (stretched film) subjected to the above-described treatment is dried according to a conventional method to become a polarizer.
The thickness of the polarizer is usually 5 to 80 μm, preferably 5 to 50 μm, and more preferably 5 to 25 μm.

  As optical properties of the polarizer, the single transmittance when measured with a single polarizer is preferably 43% or more, and more preferably in the range of 43.3 to 45.0%. Moreover, it is preferable that the orthogonal transmittance measured by superposing two polarizers described above so that the absorption axes of the two polarizers are 90 ° to each other is smaller, and practically 0.00 % Or more and 0.050% or less is preferable, and 0.030% or less is more preferable. The degree of polarization is preferably 99.90% or more and 100% or less for practical use, and particularly preferably 99.93% or more and 100% or less. Even when measured as a polarizing plate, it is preferable to obtain optical characteristics substantially equivalent to this.

  This polarizer can be obtained by the methods described in JP-A-2006-293275, JP-A-2009-98653, JP-A-2001-350021, and JP-A-2001-141926.

Further, the polarizing plate used for color control as described above preferably has a polarizing plate hue chromaticity of a ^* > 0, and a ^* > 1 when the C light source is transmitted. More preferably, a ^* > 2 is even more preferable. This is because the chromaticity of the display device is brought close to red. The upper limit value is not particularly limited, and may be 20, 15, 13, 10, or 8, for example. Here, the C light source is “auxiliary illuminant C” described in JIS Z 8720: 2012, and has a color temperature of 6774 Kelvin.

(Polarizing plate protective film)
As the polarizing plate protective film, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth) acrylic resins, cyclic Examples thereof include polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof.

  Cellulose resin is an ester of cellulose and fatty acid. Specific examples of the cellulose ester resin include triacetyl cellulose, diacetyl cellulose, tripropyl cellulose, dipropyl cellulose, and the like. Among these, triacetyl cellulose is particularly preferable. Many products of triacetylcellulose are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available products of triacetyl cellulose include trade names “UV-50”, “UV-80”, “SH-80”, “TD-80U”, “TD-TAC”, “ UZ-TAC "," KC series "manufactured by Konica, and the like.

  Specific examples of the cyclic polyolefin resin are preferably norbornene resins. The cyclic olefin-based resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers), And the graft polymer which modified these with unsaturated carboxylic acid or its derivative (s), and those hydrides, etc. are mentioned. Specific examples of the cyclic olefin include norbornene monomers.

  Various products are commercially available as the cyclic polyolefin resin. Specific examples include the product names “ZEONEX” and “ZEONOR” manufactured by ZEON CORPORATION, the product name “ARTON” manufactured by JSR Corporation, the product name “TOPAS” manufactured by TICONA, and the product rules manufactured by Mitsui Chemicals, Inc. “APEL” may be mentioned.

  Any appropriate (meth) acrylic resin can be adopted as the (meth) acrylic resin. For example, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester- (Meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer (MS resin, etc.), a polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, Methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.). Preferably, poly (meth) acrylic acid C1-6 alkyl such as poly (meth) acrylate methyl is used. More preferred is a methyl methacrylate-based resin containing methyl methacrylate as a main component (50 to 100% by mass, preferably 70 to 100% by mass).

  Specific examples of (meth) acrylic resins include (meth) acrylic resins having a ring structure in the molecule described in, for example, Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and JP-A-2004-70296. And a high Tg (meth) acrylic resin system obtained by intramolecular crosslinking or intramolecular cyclization reaction.

  As the (meth) acrylic resin, a (meth) acrylic resin having a lactone ring structure can also be used. It is because it has high mechanical strength by high heat resistance, high transparency, and biaxial stretching.

  Although the thickness of a protective film can be set suitably, generally it is about 1-80 micrometers from points, such as workability, such as intensity | strength and handling, and thin-layer property. 1-60 micrometers is especially preferable, 5-40 micrometers is more preferable, and 5-25 micrometers is still more preferable.

<Backlight unit>
The brightness enhancement film or the optical sheet member can be used in combination with a backlight unit in a liquid crystal display device. The backlight unit includes at least a blue light having an emission center wavelength in a wavelength band of 430 to 500 nm, a green light having an emission center wavelength in a wavelength band of 500 to 600 nm, and a peak of emission intensity in a wavelength band of 600 to 700 nm. What is necessary is just to provide the light source which light-emits red light which has one part.
The above-described backlight unit includes a reflecting member that converts and reflects the polarization state of light emitted from the above-described light source and reflected by the above-described brightness enhancement film or the above-described optical sheet member at the rear of the above-described light source. It is also preferable.

The backlight may be of an edge light type or a direct type using a light guide plate or a reflection plate as a constituent member, but the backlight unit emits light from the light source at the rear of the light source. It is preferable to provide a reflecting member that converts and reflects the polarization state of the light reflected by the optical sheet member. There is no restriction | limiting in particular as such a reflecting member, A well-known thing can be used, and it is described in patent 3416302 gazette, patent 3363565 gazette, patent 4091978 gazette, patent 3448626 gazette, etc., these gazettes Are incorporated into the present invention.
The light source of the backlight includes a blue light emitting diode that emits the blue light described above, and a wavelength that includes the fluorescent material that emits the green light and the red light when the blue light of the blue light emitting diode is incident. It is preferable to have a conversion member.
As the light source of the backlight, the blue light emitting diode that emits the blue light described above, the green light emitting diode that emits the green light described above, and the red light emitting diode that emits the red light described above may be used.
The light source of the backlight may be a white light source such as a white LED (Light Emitting Diode).

Examples of fluorescent materials include yttrium / aluminum / garnet yellow phosphors and terbium / aluminum / garnet yellow phosphors. The fluorescence wavelength of the fluorescent material can be controlled by changing the particle diameter of the phosphor.
The liquid crystal display device of the present invention includes a blue light emitting diode that emits the blue light and a fluorescent material that emits the green light and the red light when the blue light of the blue light emitting diode is incident. It is a quantum dot member (for example, a quantum dot sheet or a bar-shaped quantum dot bar), and the quantum dot member is preferably disposed between the optical sheet member and the blue light source. There is no restriction | limiting in particular as such a quantum dot member, Although a well-known thing can be used, For example, Unexamined-Japanese-Patent No. 2012-169271, SID'12 DIGEST p. 895, etc., and the contents of these documents are incorporated in the present invention. As such a quantum dot sheet, QDEF (Quantum Dot Enhancement Film, manufactured by Nanosys) can be used.

  The preferred emission center wavelengths of the light of each color emitted by the backlight unit are as follows. The blue light preferably has an emission center wavelength in a wavelength band of 440 to 470 nm. The green light preferably has an emission center wavelength in a wavelength band of 520 to 570 nm. The red light preferably has an emission center wavelength in a wavelength band of 600 to 640 nm.

It is preferable that the full widths at half maximum of the blue light, the green light, and the red light are 100 nm or less.
The blue light emitted from the backlight unit preferably has an emission intensity peak with a half-value width of 80 nm or less, more preferably an emission intensity peak with a half-value width of 70 nm or less, and a half-value width of 30 nm or less. It is particularly preferable to have a peak of emission intensity as follows.
The green light emitted from the backlight unit preferably has an emission intensity peak with a half-value width of 80 nm or less, more preferably an emission intensity peak with a half-value width of 70 nm or less, and a half-value width of 60 nm or less. It is particularly preferable to have a peak of emission intensity as follows.
The red light emitted from the backlight unit preferably has an emission intensity peak with a half-value width of 80 nm or less, more preferably an emission intensity peak with a half-value width of 70 nm or less, and a half-value width of 60 nm or less. It is particularly preferable to have a peak of emission intensity as follows.

Difference (reflection) between the emission center wavelength of blue light, green light and red light of the backlight unit (wavelength that gives the peak of emission intensity) and the reflection center wavelength of each color in the brightness enhancement film (wavelength that gives the peak of reflectance) As a result of the inventor's research, the center wavelength-emission center wavelength) is preferably within ± 50 nm and more preferably within ± 25 nm for blue and green light.
On the other hand, with respect to red light, 0 to 75 nm is preferable from the viewpoint of suppressing oblique color change, more preferably 0 to 50 nm, and further preferably 10 to 30 nm.
In the case where the emission color of the backlight unit is controlled as described above, the front chromaticity of the backlight unit is preferably a ^* > 8, more preferably a ^* > 12. It is more preferable that a ^* > 16, and it is further preferable that a ^* > 20. This is to bring the chromaticity of the display device to the red direction. The upper limit value is not particularly limited, and may be 50, 30, or 20, for example.

  In addition, the backlight unit preferably includes a known diffusion plate, diffusion sheet, prism sheet (for example, BEF), and a light guide. Other members are also described in Japanese Patent No. 3416302, Japanese Patent No. 3363565, Japanese Patent No. 4091978, Japanese Patent No. 3448626, and the like.

  It is also preferable that the backlight unit includes two prism sheets whose prism directions are substantially parallel to each other. This is because the front luminance of the liquid crystal display device can be further improved. The direction in which the prisms of the two prism sheets are substantially parallel means that the angle formed by the prisms of the two prism sheets is within ± 5 °. Note that the prism sheet has a plurality of protrusions (in the present specification, these protrusions are also referred to as prisms) extending in one direction within the surface of the prism sheet. The directions in which the plurality of prisms arranged in are extended are parallel. The direction of the prism refers to the extending direction of a plurality of prisms arranged in a row. The front luminance can be increased by using two prism sheets whose prism directions are substantially parallel to each other, rather than two prism sheets whose prism directions are substantially perpendicular to each other. In addition, the same effect can be acquired also when combining any of the above-mentioned light sources.

<Method of bonding optical sheet member to liquid crystal display device>
As a method for bonding the brightness enhancement film or the optical sheet member to the liquid crystal display device, a known method can be used. In addition, a roll-to-panel manufacturing method can be used, which is preferable for improving productivity and yield. The roll-to-panel manufacturing method is described in JP2011-48381, JP2009-175653, JP4628488, JP4729647, WO2012 / 014602, WO2012 / 014571, etc. It is not limited.

<Layer that changes the polarization state of light>
It is preferable to dispose a layer that changes the polarization state of light between the outermost light reflecting layer of the brightness enhancement film and the backlight unit. The layer that changes the polarization state of the light functions as a layer that changes the polarization state of the light reflected from the light reflection layer, can improve the brightness, reduce the color change, and reduce coating unevenness. is there. Examples of the layer that changes the polarization state of light include a polymer layer having a refractive index higher than that of the air layer. Examples of the polymer layer having a refractive index higher than that of the air layer include a hard coat (HC) treatment layer, an antiglare ( Various low reflection layers such as AG) treatment layer and low reflection (AR) treatment layer, triacetyl cellulose (TAC) film, acrylic resin film, cycloolefin polymer (COP) resin film, stretched PET film and the like. The layer that changes the polarization state of light may also serve as a support. The relationship between the average refractive index of the layer that changes the polarization state of the light reflected from the light reflecting layer and the average refractive index of the outermost light reflecting layer is as follows:

0 <| average refractive index of the layer that changes the polarization state of light−average refractive index of the outermost light reflecting layer |
0 <| the average refractive index of the layer that changes the polarization state of the light−the average refractive index of the outermost light reflecting layer | more preferably 0.4 <0 <| the average of the layer that changes the polarization state of the light Refractive index-average refractive index of the outermost light reflecting layer | <0.2 is more preferable.
The layer that changes the polarization state of light may be integrated with the brightness enhancement film, or may be provided separately from the brightness enhancement film.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

<Production of λ / 4 plate>
First, a cellulose ester support T1 for a λ / 4 plate was prepared.
(Preparation of cellulose ester solution A-1)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose ester solution A-1.
――――――――――――――――――――――――――――――――――
Composition of cellulose ester solution A-1 ――――――――――――――――――――――――――――――――――
-Cellulose acetate (degree of acetylation 2.86) 100 parts by mass-Methylene chloride 320 parts by mass-Methanol 83 parts by mass-1-butanol 3 parts by mass-Triphenyl phosphate 7.6 parts by mass-Biphenyl diphenyl phosphate 3.8 Mass part ――――――――――――――――――――――――――――――――――

(Preparation of matting agent dispersion B-1)
The following composition was charged into a disperser and stirred to dissolve each component to prepare a matting agent dispersion B-1.
――――――――――――――――――――――――――――――――――
Composition of Matting Agent Dispersion B-1 ――――――――――――――――――――――――――――――――――
・ Silica particle dispersion (average particle size 16 nm)
"AEROSIL R972", Nippon Aerosil Co., Ltd. 10.0 parts by mass-Methylene chloride 72.8 parts by mass-Methanol 3.9 parts by mass-Butanol 0.5 parts by mass-Cellulose ester solution A-1 10.3 parts by mass ――――――――――――――――――――――――――――――――――

(Preparation of UV absorber solution C-1)
The following composition was put into another mixing tank and stirred while heating to dissolve each component to prepare an ultraviolet absorber solution C-1.
――――――――――――――――――――――――――――――――――
Composition of UV absorber solution C-1 ――――――――――――――――――――――――――――――――――
UV absorber (UV-1 below) 10.0 parts by weight UV absorber (UV-2 below) 10.0 parts by weight Methylene chloride 55.7 parts by weight Methanol 10 parts by weight Butanol 1.3 parts by weight・ Cellulose ester solution A-1 12.9 parts by mass ――――――――――――――――――――――――――――――――――

(Preparation of cellulose ester support T1)
In a mixture of 94.6 parts by mass of cellulose acylate solution A-1 and 1.3 parts by mass of matting agent dispersion B-1, ultraviolet absorber (UV-1) and ultraviolet rays per 100 parts by mass of cellulose acylate An ultraviolet absorbent solution C-1 was added so that the amount of the absorbent (UV-2) was 1.0 part by mass, and each component was dissolved by stirring sufficiently while heating to prepare a dope. The obtained dope was heated to 30 ° C., and cast on a mirror surface stainless steel support, which was a drum having a diameter of 3 m, through a casting Giuser. The surface temperature of the support was set to −5 ° C., and the coating width was 1470 mm. The cast dope film was dried on the drum by applying a drying air of 34 ° C. at 150 m ³ / min, and peeled off from the drum with a residual solvent of 150%. During peeling, 15% stretching was performed in the transport direction (longitudinal direction). Thereafter, the film is conveyed while being gripped by a pin tenter (a pin tenter described in FIG. 3 of JP-A-4-1009) at both ends in the width direction (direction perpendicular to the casting direction), and stretched in the width direction. No processing was performed. Furthermore, it dried further by conveying between the rolls of the heat processing apparatus, and manufactured the cellulose acylate support body T1. The produced long cellulose acylate support T1 had a residual solvent amount of 0.2%, a thickness of 60 μm, and Re and Rth at 550 nm of 0.8 nm and 40 nm, respectively.

(Production of liquid crystal layer of λ / 4 plate)
PVA PVA-103 manufactured by Kuraray Co., Ltd. was dissolved in pure water. The concentration and the coating amount of the solution were adjusted so that the dry film thickness was 0.5 μm, and bar-coated on the cellulose acylate support T1 prepared above. Thereafter, the coating film was heated at 100 ° C. for 5 minutes. Further, this surface was rubbed to obtain an alignment layer.
Subsequently, a solute having the following composition was dissolved in MEK (methyl ethyl ketone) to prepare a coating solution. This coating solution was adjusted so that the concentration and the coating amount were 1 μm in dry film thickness, and bar-coated on the alignment layer. Thereafter, the solvent was kept at 85 ° C. for 2 minutes to evaporate the solvent, and then heat-aged at 100 ° C. for 4 minutes to obtain a uniform alignment state. The discotic compound was aligned perpendicular to the support plane.
Thereafter, this coating film was kept at 80 ° C. and irradiated with ultraviolet rays using a high-pressure mercury lamp in a nitrogen atmosphere to produce a λ / 4 plate.

――――――――――――――――――――――――――――――――――
Solute composition of coating solution for liquid crystal layer preparation ――――――――――――――――――――――――――――――――――
Discotic liquid crystal compound 1 35 parts by mass Discotic liquid crystal compound 2 35 parts by mass alignment aid (compound 3) 1 part by weight alignment aid (compound 4) 1 part by mass polymerization initiator (compound 5) 3 parts by mass ――――――――――――――――――――――――――――――

<Preparation of retardation element I>
Styrene-maleic anhydride copolymer (“Dylark D332”, manufactured by Nova Chemical Co., Tg = 131 ° C.) as a material having a negative intrinsic birefringence value, and norbornene-based resin (trade name: ZEONOR1020, Nippon Zeon) as a transparent resin material Manufactured by Tg = 105 ° C.). First, the melted norbornene resin and the styrene-maleic anhydride copolymer were respectively stored in the extruders of the extrusion dies in which the two extruders were integrally combined with the extrusion die. The extrusion flow path of the above-described extruder containing the norbornene-based resin is branched into two, and the norbornene-based resin extruded from the branched flow path is styrene-maleic anhydride copolymer extruded from another extruder. The polymer was sandwiched to form a three-layer laminate inside the extrusion die. In addition, a filter is disposed at a communication port to the extrusion die of the two extruders, and the above-described norbornene resin and styrene-maleic anhydride copolymer are passed through the filter and then extruded into the extrusion die. Thus, a laminate having a three-layer structure was obtained. The thickness unevenness of this laminate was measured using a scanning thickness meter. The measurement was performed by continuously scanning in the longitudinal direction of the laminate. The obtained laminate had an average thickness of 300 μm, and the thickness unevenness was 2.5% with respect to the above-mentioned thickness average.

Next, the laminate is sequentially fed into a uniaxial stretching device in the longitudinal direction parallel to the conveying direction of zone heating and a tenter stretching device (uniaxial stretching in the lateral direction perpendicular to the conveying direction) to sequentially perform biaxial stretching. Thus, a retardation element I was produced. The stretching temperature was 140 ° C. for both the above-described longitudinal stretching and lateral stretching, and the stretching ratio was 1.8 times for longitudinal stretching and 1.5 times for lateral stretching.
When the average thickness of the obtained retardation element I was 120 μm and the refractive index and retardation were measured using an automatic birefringence measuring device KOBRA-21SDH (manufactured by Oji Scientific Instruments), the refractive index in the plane direction was nx = The refractive index in the thickness direction was 1.5732, ny = 1.5731, and nz = 1.757. Retardation was 10 nm for Re and −300 nm for Rth.

<Formation of optical laminate E>
As the alignment layer, Sunever SE-130 (Nissan Chemical Co., Ltd.) was dissolved in N-methylpyrrolidone. The above solution was bar-coated on Corning glass 7059 with the concentration and coating amount adjusted to a dry film thickness of 0.5 μm. The coating film was heated at 100 ° C. for 5 minutes, and further heated at 250 ° C. for 1 hour. Thereafter, the surface was rubbed to obtain an alignment layer.
Subsequently, a solute having the following composition was dissolved in MEK to prepare a coating solution for forming the light reflection layer E containing a discotic liquid crystal compound. After adjusting the concentration and the coating amount of this coating solution so that the film thickness becomes 2.4 μm, applying the bar on the alignment layer, holding the solvent at 70 ° C. for 2 minutes, and evaporating the solvent Heat aging was performed at 100 ° C. for 4 minutes to obtain a uniform alignment state.
Thereafter, this coating film was kept at 45 ° C., and irradiated with ultraviolet rays using a high-pressure mercury lamp in a nitrogen atmosphere to produce an optical laminate E including a light reflection layer E. The film thickness of the light reflection layer E was 2.4 μm. As a result of measuring the pitch of cholesteric using AXOSCAN of AXOMETRIX, the reflection wavelength was 450 nm to 510 nm.

――――――――――――――――――――――――――――――――――
Solute composition of coating solution for forming light reflection layer E ――――――――――――――――――――――――――――――――――
Discotic liquid crystal compound 1 56 parts by mass Discotic liquid crystal compound 2 14 parts by mass alignment aid (compound 3) 1 part by weight alignment aid (compound 4) 1 part by mass polymerization initiator (compound 5) 3 parts by mass chiral agent (compound 6) 2.5 parts by mass ―――――――――――――――――――――――――――――――――

<Preparation of optical laminate A>
First, a terminal fluorinated alkyl group-containing polymer (compound A) having an optically active site was obtained by the procedure described in Japanese Patent No. 4570377 [0065]. Specifically, Compound A was obtained as follows.
To a four-necked flask equipped with a condenser, a thermometer, a stirrer, and a dropping funnel, a fluorinated solvent AK-225 (Asahi Glass Co., Ltd., 1,1,1,2,2-pentafluoro-3,3-dichloropropane: 1 , 1,2,2,3-pentafluoro-1,3-dichloropropane = 1: 1.35 (molar ratio) mixed solvent)) 50 parts by mass, a reactive chiral agent (compound) having optical activity of the following structure 7. In the formula, * indicates an optically active site) 5.22 parts by mass are charged, the reaction vessel is heated to 45 ° C., and then 10 mass of diperfluoro-2-methyl-3-oxahexanoyl peroxide / AK225 6.58 parts by mass of a% solution was added dropwise over 5 minutes. After completion of dropping, the reaction is carried out in a nitrogen stream at 45 ° C. for 5 hours, and then the product is concentrated to 5 ml, reprecipitated with hexane, and dried to contain a terminal fluorinated alkyl group-containing polymer. (Compound A) 3.5 parts by mass (yield 60%) was obtained.
When the molecular weight of the obtained polymer was measured using GPC and THF (tetrahydrofuran) as a developing solvent, Mn = 4,000 (Mw / Mn = 1.77) and the fluorine content was measured to determine the fluorine content. Was 5.89% by mass.

An alignment film coating solution consisting of 10 parts by weight of polyvinyl alcohol and 371 parts by weight of water was applied to a glass 7059 manufactured by Corning Co., Ltd. on one side of the glass and dried to form an alignment film having a thickness of 1 μm. Next, a rubbing treatment was performed on the alignment film continuously in a direction parallel to the longitudinal direction of the glass.
On the alignment film, a composition having the following composition was applied using a bar coater, dried at room temperature for 10 seconds, heated in an oven at 100 ° C. for 2 minutes (alignment aging), and further irradiated with ultraviolet rays for 30 seconds. An optical laminate A having a light reflection layer A having a thickness of 5.0 μm was produced.

――――――――――――――――――――――――――――――――――
Composition for forming the light reflection layer A -----------
Compound 8 8.2 parts by mass Compound 9 0.3 parts by mass Terminally fluorinated alkyl group-containing polymer having optically active site (Compound A)
1.9 parts by mass Methyl ethyl ketone 24.0 parts by mass ―――――――――――――――――――――――――――――――――

When the cross section of the light reflecting layer A composed of the cholesteric liquid crystal layer was observed with a scanning electron microscope, it had a structure having a helical axis in the normal direction of the layer and continuously changing the cholesteric pitch. Here, regarding the cholesteric pitch, when the cross section of the cholesteric liquid crystal layer is observed with a scanning electron microscope, the width in the layer normal direction of the light portion and the dark portion repeated twice (brightness, darkness, and darkness) is counted as one pitch.
If the surface side with a small cholesteric pitch is defined as the x plane and the surface with the large surface is defined as the y plane, the result calculated from the measured cholesteric pitch is that the cholesteric reflection wavelength near the x plane is 410 nm, and the cholesteric wavelength near the y plane is The reflection wavelength of was 700 nm.

<Preparation of optical laminates C1, C2, C3>
In the production of the optical laminate A, the thickness of the cholesteric liquid crystal layer was 3.5 μm, and the amount of polymer (compound A) added, the aging temperature, and the ultraviolet irradiation conditions were changed, as in the optical laminate A. Optical laminated bodies C1, C2, and C3 having light reflecting layers C1, C2, and C3 were produced.
When the cross sections of the optical laminates C1, C2, and C3 were observed with a scanning electron microscope, all had a helical axis in the layer normal direction and a structure in which the cholesteric pitch was continuously changed in the thickness direction. It was.
Moreover, as a result of measuring the transmittance | permeability of a cholesteric liquid crystal layer similarly to the optical laminated body A, C1 had 500-680 nm, C2 had 500-700 nm, and C3 had a reflective wavelength of 530-700 nm.

<Production of brightness enhancement film (corresponding to optical sheet members 1 to 5 and 11)>
A λ / 4 plate, each light reflection layer, or retardation element I was used in the combinations shown in Table 1, and each was bonded to each other with an adhesive material to produce a brightness enhancement film. In addition, the optical laminated body was transferred from the support glass using an adhesive material, and only the light reflecting layer composed of a cholesteric liquid crystal layer was used as the configuration of the brightness enhancement film. The λ / 4 plate was bonded with a light reflecting layer and an adhesive on the liquid crystal layer side.

<Preparation of λ / 4 plate integrated light reflection layer TC1>
After passing the triacetyl cellulose film through a dielectric heating roll having a temperature of 60 ° C. and raising the film surface temperature to 40 ° C., an alkaline solution having the composition shown below was applied to the band surface of the film using a bar coater. The coating was carried out for 10 seconds under a steam far-infrared heater manufactured by Noritake Company Limited, which was applied at an amount of 14 ml / m ² and heated to 110 ° C. Subsequently, 3 ml / m ^{2 of} pure water was applied using the same bar coater. Next, washing with a fountain coater and draining with an air knife were repeated three times, and then transported to a drying zone at 70 ° C. for 10 seconds to dry, thereby producing an alkali saponified triacetyl cellulose film.

──────────────────────────────────
Alkaline solution composition ──────────────────────────────────
Potassium hydroxide 4.7 parts by weight Water 15.8 parts by weight Isopropanol 63.7 parts by weight Surfactant SF-1: C ₁₄ H ₂₉ O (CH ₂ CH ₂ O) ₂₀ H 1.0 part by weight Propylene glycol 14. 8 parts by mass ──────────────────────────────────

  An alignment film coating solution (A) having the following composition was continuously applied with a # 14 wire bar on the surface of the triacetylcellulose film which had been subjected to alkali saponification treatment. The alignment film was formed by drying with warm air of 60 ° C. for 60 seconds and further with warm air of 100 ° C. for 120 seconds. The degree of saponification of the modified polyvinyl alcohol used was 96.8%.

──────────────────────────────────
Composition of coating liquid for alignment film (A) ――――――――――――――――――――――――――――――――――
Denatured polyvinyl alcohol 10 parts by weight Water 308 parts by weight Methanol 70 parts by weight Isopropanol 29 parts by weight Photopolymerization initiator (Irgacure 2959, manufactured by BASF) 0.8 parts by weight ―――――――――――― ――――――――――――――――――――――

  The alignment film thus prepared was continuously rubbed. At this time, the longitudinal direction of the long film and the transport direction were parallel, and the angle formed by the longitudinal direction of the film and the rotation axis of the rubbing roller was about 45 °.

Subsequently, a solute having the following composition was dissolved in MEK to prepare a coating solution. The coating solution was bar-coated on the alignment layer by adjusting the concentration and coating amount so that the dry film thickness was 1.0 μm. The coating film was heat-aged at 80 ° C. for 1 minute to obtain a uniform alignment state. Thereafter, this coating film was held at 75 ° C., and irradiated with ultraviolet rays using a high-pressure mercury lamp in a nitrogen atmosphere to form a λ / 4 plate on the triacetyl cellulose film to produce a λ / 4 plate Tλ1. . When the retardation of the obtained film was measured, all were 128 nm.
──────────────────────────────────
Solute composition of coating solution for liquid crystal layer formation on λ / 4 plate──────────────────────────────────
Discotic liquid crystal compound 1 80 parts by mass Discotic liquid crystal compound 2 20 parts by mass alignment aid 1 0.9 parts by mass alignment aid 2 0.08 parts by mass surfactant 1 0.075 parts by mass polymerization initiator 3 parts by mass polymerization 10 parts by weight of monomer --------------------

In description of a / b = 98/2 in the said compound, a shows that it is 98 mass% and b is 2 mass%.

On the above-mentioned λ / 4 plate Tλ1, a light reflecting layer D was formed as a light reflecting layer formed by fixing a cholesteric liquid crystal phase using a discotic liquid crystal compound as a cholesteric liquid crystal material by the following method.
A solute having the following composition was dissolved in MEK to prepare a coating solution for forming the light reflection layer D containing a discotic liquid crystal compound. This coating solution is bar-coated on the above-mentioned λ / 4 plate with the concentration and coating amount adjusted so that the dry film thickness is 2.4 μm, and aging is performed at 110 ° C. for 1 minute. Thus, a uniform alignment state was obtained. Thereafter, this coating film is kept at 45 ° C., and irradiated with ultraviolet rays using a high-pressure mercury lamp in a nitrogen atmosphere to directly apply the light reflecting layer D having a reflection band of 630 to 710 on the λ / 4 plate Tλ1. Thus, a λ / 4 plate integrated light reflection layer TC1 was produced.

──────────────────────────────────
Composition for forming light reflecting layer D -----------------------------
Discotic liquid crystal compound 1 80 parts by weight Discotic liquid crystal compound 2 20 parts by weight Surfactant 1 0.45 parts by weight Polymerization initiator 1 3 parts by weight chiral agent (Compound 6) 3.5 parts by weight ─────── ────────────────────────────

<Preparation of optical laminate B>
Among the production of the optical laminate A, a long cellulose acylate film (TD80UL (manufactured by Fuji Film Co., Ltd.) is used as a support, the film thickness of the cholesteric liquid crystal layer is 3.5 μm, and a polymer (compound A) is added. An optical laminate B was prepared in the same manner as the optical laminate A except that the amount, aging temperature, and ultraviolet irradiation conditions were changed.
When the cross section of this optical laminated body B was observed with the scanning electron microscope, it had the structure which had the helical axis in the layer normal direction, and the cholesteric pitch changed continuously in the thickness direction.
Moreover, as a result of measuring the transmittance of the cholesteric liquid crystal layer in the same manner as in the optical laminate A, it had a reflection wavelength of 410 to 580 nm.

<Preparation of brightness enhancement film (for optical sheet member 6)>
In the configuration shown in Table 1, the λ / 4 plate-integrated light reflection layer TC1 and the optical laminate B were roll-to-roll bonded with an acrylic UV curable adhesive to produce a brightness enhancement film. The optical laminate B was transferred from a cellulose acylate film, and only the cholesteric liquid crystal layer (light reflection layer B) was used.

<Preparation of Polarizing Plate 1 (Uncolored Polarizing Plate)>
A 75 μm thick polyvinyl alcohol film (Kuraray Co., Ltd., 9 × 75RS) is continuously conveyed by a guide roll, immersed in a 30 ° C. water bath to swell 1.5 times, and stretched to double the length. After setting it as a draw ratio, it was immersed in a dyeing bath (30 ° C.) containing iodine and potassium iodide for dyeing treatment and drawing treatment to obtain a draw ratio of 3 times. The obtained film was crosslinked in an acidic bath (60 ° C.) to which boric acid and potassium iodide were added and stretched to a draw ratio of 6.5 times and dried at 50 ° C. for 5 minutes to obtain a polarizing film. Obtained. At that time, the concentration of potassium iodide was set to 1%. A polarizing plate 1 was obtained by adhering a triacetyl cellulose film having a thickness of 80 μm to both sides via a polyvinyl alcohol adhesive layer.
About this polarizing plate 1, the hue chromaticity in C light source measured using JASCO Corporation automatic polarizing film measuring apparatus VAP-7070 was a ^* =-1.5.

<Preparation of polarizing plate 2 (red colored polarizing plate)>
A 75 μm thick polyvinyl alcohol film (Kuraray Co., Ltd., 9 × 75RS) is continuously conveyed by a guide roll, immersed in a 30 ° C. water bath to swell 1.5 times, and stretched to double the length. After setting it as a draw ratio, it was immersed in a dyeing bath (30 ° C.) containing iodine and potassium iodide for dyeing treatment and drawing treatment to obtain a draw ratio of 3 times. The obtained film was crosslinked in an acidic bath (60 ° C.) to which boric acid and potassium iodide were added and stretched to a draw ratio of 6.5 times and dried at 50 ° C. for 5 minutes to obtain a polarizing film. Obtained. At that time, the concentration of potassium iodide was 3%. A polarizing plate 2 was obtained by adhering a triacetyl cellulose film having a thickness of 80 μm to both sides via a polyvinyl alcohol adhesive layer.
About this polarizing plate 2, the hue chromaticity in the C light source measured using JASCO Corporation automatic polarization film measuring apparatus VAP-7070 was a ^* = 0.5.

<Preparation of Polarizing Plate 1B>
The polarizing plate 1B was produced without adhering one of the triacetyl cellulose films adhered to both surfaces in the production of the polarizing plate 1. About this polarizing plate 1B, the hue chromaticity in the C light source measured using JASCO Corporation automatic polarization film measuring apparatus VAP-7070 was a ^* =-1.5.

<Production of optical sheet members 1 to 6>
Optical sheet members 1 to 6 and 11 were manufactured by bonding any one of the polarizing plate 1, the polarizing plate 2, and the polarizing plate 1 </ b> B to the brightness enhancement film in the combinations shown in Table 1. In the production of the optical sheet members 1 to 5 and 11, the λ / 4 plate of the brightness enhancement film was bonded to one triacetyl cellulose film surface of the polarizing plate at the time of bonding. When manufacturing the optical sheet member 6, a λ / 4 plate (triacetyl cellulose film surface) was bonded to the surface side of the polarizer to which the triacetyl cellulose film was not bonded.
In addition, each said member was prepared as a long thing, and each was bonded together by the roll toe roll on both surfaces of the polarizer.

<Formation of wavelength conversion sheet 1>
With reference to Japanese Patent Application Laid-Open No. 2012-169271, the wavelength of fluorescent light emission when green light from a blue light emitting diode is incident is green light having a center wavelength of 535 nm and a half width of 40 nm and red light having a center wavelength of 630 nm and a half width of 40 nm. Conversion sheet 1 (quantum dot material (G, R)) was formed.

<Formation of wavelength conversion sheet 2 (strong red light)>
In the wavelength conversion sheet 1, except that the quantum dot material R is increased, when the blue light of the blue light emitting diode is incident, green light having a center wavelength of 535 nm, a half width of 40 nm, a center wavelength of 630 nm, A wavelength conversion sheet 2 (quantum dot materials (G, R)) that emits red light with a half-value width of 45 nm was formed.

<Manufacture of liquid crystal display devices>
A commercially available liquid crystal display device (trade name TH-L42D2 manufactured by Panasonic Corporation) was disassembled, the display-side polarizing plate was changed to the polarizing plate 1, and the backlight unit was changed to the following RGB narrow-band backlight unit. Further, as shown in Table 2, the backlight unit is changed to the following RGB narrow-band backlight unit using optical sheet members 1 to 6, 11, polarizing plate 1 or polarizing plate 2, as shown in Table 2. And the liquid crystal display device of Examples 1-6, the comparative example 1, and the reference examples 1-4 was manufactured.
The RGB narrow-band backlight unit includes a blue light-emitting diode (Nichia B-LED, main wavelength 465 nm, half-value width 20 nm) as a light source. What provided the conversion sheet 1 or 2 was used.
Using a measuring instrument (EZ-Contrast 160, manufactured by ELDIM), the front color of the RGB narrow-band backlight unit was evaluated. In combination with the wavelength conversion sheet 1, a ^* = 6, and with the wavelength conversion sheet 2. In combination, a ^* = 9.

<Evaluation of liquid crystal display device>
The obtained liquid crystal display devices of Examples, Comparative Examples, and Reference Examples were left in a room controlled at 25 ° C. and 60% RH for one week, and then evaluated as follows. The results are shown in Table 2.
(Slant color evaluation)
Using a measuring machine (EZ-Contrast 160, manufactured by ELDIM), the color was evaluated in white display. As the chromaticity a ^** , data at polar angles of 0 to 60 degrees and omnidirectional angles were used.
(sensory evaluation)
The polar angle of 0 to 60 degrees and the omnidirectional angle of the liquid crystal display device were visually observed and evaluated according to the following criteria.
5: Hue change is small and there is no problem in display performance.
4: Although there is some hue change, there is no problem in display performance.
3: There is a problem of hue change and display performance is a concern.
2: The hue change is large, which is a problem in display performance.
1: The hue change is very large, which is very problematic in display performance.

From the results shown in Table 2, in Reference Example 2 using Polarizing Plate 2, the overall color is moving in the red direction (a ^* increase direction) compared to Reference Example 1 using Polarizing Plate 1. I understand. Moreover, in the reference example 3 using the wavelength conversion sheet 2, it turns out that the whole color is moving to the red direction (a ^* increase direction) compared with the reference example 1 using the wavelength conversion sheet 1. FIG. In Reference Example 4 using the polarizing plate 2 and the wavelength conversion sheet 2, it can be seen that the whole color is further moved in the red direction (a ^* increase direction). Among Comparative Example 1 and Examples 1 to 5 which are examples using an optical sheet member including a brightness enhancement film, Comparative Example 1 has a color shift in the green direction, and the result of sensory evaluation is deteriorated. In Examples 1 to 5 in which the entire color is adjusted in the red direction (a ^* increase direction) by the polarizing plate 2 and / or the wavelength conversion sheet 2, the result of sensory evaluation is good.

DESCRIPTION OF SYMBOLS 1 Backlight side polarizing plate 10 Support body 11 Brightness improvement film 12 (lambda) / 4 board 13 Reflective polarizer 14a First light reflection layer 14b Second light reflection layer 14c Third light reflection layer 15 Polarizer 16 Polarizing plate protection Film 20 Adhesive layer (adhesive)
21 Optical sheet member 31 Backlight unit 41 Thin layer transistor substrate 42 Liquid crystal cell 43 Color filter substrate 44 Display side polarizing plate 51 Liquid crystal display device

Claims (16)

A liquid crystal display device including a display side polarizing plate, a liquid crystal cell, a backlight side polarizing plate, and a backlight unit in this order,
Including a brightness enhancement film between the backlight side polarizing plate and the backlight unit;
The brightness enhancement film includes a λ / 4 plate and a reflective polarizer in this order from the backlight side polarizing plate side,
The reflective polarizer includes a light reflecting layer formed by fixing at least one cholesteric liquid crystal phase,
A liquid crystal display device in which chromaticity a ^* of image light during white display of the liquid crystal display device is −3 <a ^* <14 at all azimuth angles of polar angles of 0 ° to 60 °. 2. One or more selected from the group consisting of the display-side polarizing plate and the backlight-side polarizing plate is a polarizing plate having a hue chromaticity a ^* > 0 when transmitted through a C light source. A liquid crystal display device according to 1. The liquid crystal display device according to claim 1, wherein a front chromaticity of the backlight unit is a ^* > 8. The liquid crystal display device according to claim 1, wherein the reflective polarizer includes a light reflection layer that reflects blue light and green light, and a red light reflection layer that reflects red light. The liquid crystal display device according to claim 4, wherein the layer reflecting blue light and green light is a broadband light reflecting layer. The liquid crystal display device according to claim 4, wherein the red light reflection layer is a light reflection layer that further reflects infrared light. The liquid crystal display device according to claim 1, wherein the reflective polarizer includes a light reflection layer that reflects green light and red light, and a blue light reflection layer that reflects blue light. The liquid crystal display device according to claim 7, wherein the layer reflecting green light and red light is a broadband light reflecting layer. The reflective polarizer includes a layer formed from a polymerizable liquid crystal composition containing a rod-like liquid crystal compound,
The spiral pitch of the cholesteric liquid crystal phase of the said layer formed from the polymeric liquid crystal composition containing a rod-shaped liquid crystal compound is changing continuously in the film thickness direction of the said layer. Liquid crystal display device. The liquid crystal display device according to claim 1, wherein the reflective polarizer includes a layer formed from a polymerizable liquid crystal composition including a discotic liquid crystal compound. The liquid crystal display device according to claim 1, wherein the λ / 4 plate is a layer formed from a polymerizable liquid crystal composition containing a discotic liquid crystal compound. The layer which changes the polarization state of light on the opposite side to the λ / 4 plate side of the reflective polarizer, and the layer which changes the polarization state of the light satisfies the following condition. The liquid crystal display device according to one item.
0 <| average refractive index of the layer that changes the polarization state of light−average refractive index of the outermost light reflecting layer | <0.8 The backlight unit is
Blue light having an emission center wavelength in a wavelength band of 430 to 500 nm;
Green light having an emission center wavelength in a wavelength band of 500 to 600 nm;
A light source that emits red light having at least a part of a peak of emission intensity in a wavelength band of 600 to 700 nm;
The said backlight unit is provided with the reflection member which converts and reflects the polarization state of the light emitted from the light source and reflected by the brightness enhancement film or the optical sheet member at the rear part of the light source. The liquid crystal display device according to any one of the above. The liquid crystal display device according to claim 13, wherein the full width at half maximum of the blue light, green light, and red light is 100 nm or less. The light source is a light source having a blue light emitting diode that emits the blue light and a fluorescent material that emits the green light and the red light when the blue light of the blue light emitting diode is incident. 14. A liquid crystal display device according to item 14. The liquid crystal display device according to claim 15, wherein the fluorescent material is a quantum dot member.

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