JP2019204085A - Optical laminate, display panel, and display device - Google Patents

Abstract

To provide: an optical laminate capable of producing a display device which offers enhanced brightness of blue color when viewed from the front, allowing for prolonging life of the display device as a result, and suppresses blue shift in images when viewed from an oblique angle; a display panel equipped with such optical laminate; the display device equipped with such optical laminate; and a transreflective film, retardation plate, and polarizer used for the display panel.SOLUTION: An optical laminate comprising a transreflective film, retardation plate, and polarizer is provided, the optical laminate being characterized in that the laminate contains a compound having an absorption at a wavelength below 480 nm, and that the transreflective film has a selective reflection wavelength in a wavelength range of 380-480 nm, inclusive.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical laminate, a display panel, and a display device.

In recent years, various display devices have been increased in size and portability, and as a result, good hues in various observation environments have been demanded.
Patent Document 1 discloses an organic electroluminescence light source device in which a change in hue due to an observation angle is suppressed.

JP 2009-231257 A

Blue is difficult to obtain high emission luminance, and generally the lifetime of the display device is determined by the blue emission lifetime. Accordingly, even if the blue light emission amount of the display element is the same, it is required to increase the visible blue light emission luminance, thereby extending the lifetime.
On the other hand, in a display device including an optical laminate having a retardation plate and a polarizer, when observed from an oblique direction, a phenomenon called “blue shift” in which the bluishness of an image becomes strong may occur.
The present invention provides a display device capable of improving the luminance of blue in frontal observation and, as a result, extending the life of the display device and suppressing the blue shift of an image when observed from an oblique direction. An object is to provide a possible optical laminate. Furthermore, the present invention provides a display panel comprising the optical laminate, a display device comprising the optical laminate, and a transflective film, a retardation plate, and a polarizer used in the display panel. Objective.

  As a result of intensive studies to solve the above problems, the present inventors have found that in an optical laminate having a transflective film, a retardation plate, and a polarizer, the optical laminate has absorption at 480 nm or less. And the semi-transmissive / semi-reflective film has a selective reflection wavelength of 380 nm or more and 480 nm.

The present invention relates to the following <1> to <18>.
<1> An optical laminate having a transflective film, a retardation plate, and a polarizer, the optical laminate contains a compound having absorption at 480 nm or less, and the transflective film is 380 nm. An optical layered body having a selective reflection wavelength of 480 nm or more.
<2> The transflective film is a liquid crystal layer having a cholesteric structure, the retardation layer and the polarizer constitute a circularly polarizing plate, and the transflective film, the retardation film and the polarizer are arranged in this order. The optical laminate according to <1>.
<3> For incident light from the side of the liquid crystal layer having a cholesteric structure, the liquid crystal layer having the cholesteric structure reflects right circularly polarized light, and the circularly polarizing plate transmits left circularly polarized light, or The optical laminate according to <2>, wherein the liquid crystal layer having a cholesteric structure reflects left circularly polarized light, and the circularly polarizing plate transmits right circularly polarized light.
<4> The optical laminate according to <2> or <3>, wherein the reflection wavelength peak of the optical laminate is located on the long wavelength side with respect to the selective reflection center wavelength of the liquid crystal layer having the cholesteric structure.
<5> The optical laminate according to any one of <2> to <4>, wherein the half-width of the reflection peak of the optical laminate is smaller than the half-width of the reflection peak of the liquid crystal layer having the cholesteric structure alone. .
<6> The optical laminate according to any one of <1> to <5>, further comprising a protective layer.
<7> Furthermore, the optical laminated body in any one of <1>-<6> which has an adhesion layer.
<8> The optical laminate according to any one of <1> to <7>, wherein the retardation plate is a quarter-wave retardation plate.
<9> The optical laminate according to any one of <1> to <7>, wherein the retardation plate is a laminate of a quarter-wave retardation plate and a half-wave retardation plate.
<10> The optical laminate according to <8> or <9>, wherein the retardation plate further includes a positive C plate.
<11> A display panel comprising the optical laminate according to any one of <1> to <10> on a light emitting surface of a display element.
<12> The display panel according to <11>, wherein the display element has a microcavity structure.
<13> The display panel according to <11> or <12>, wherein the difference between the blue emission peak wavelength of the display element and the reflection peak wavelength of the optical laminate is 20 nm or less.
<14> A display device comprising the display panel according to any one of <11> to <13>.
<15> The display device according to <14>, wherein the display device is an organic electroluminescence display device.
<16> A retardation plate used for the display panel according to any one of <11> to <13>.
<17> A polarizer used for the display panel according to any one of <11> to <13>.
<18> A transflective film used for the display panel according to any one of <11> to <13>.

  According to the present invention, in frontal observation, the luminance of blue can be improved, and as a result, the lifetime of the display device can be extended, and the blue shift of the image is suppressed when observed from an oblique direction. Can be provided. Furthermore, according to this invention, the display panel provided with the said optical laminated body, the display apparatus provided with this optical laminated body, the transflective film used for the said display panel, a phase difference plate, and a polarizer are provided. be able to.

It is sectional drawing which shows an example of the optical laminated body of this invention typically. It is sectional drawing which shows typically another example of the optical laminated body of this invention. It is sectional drawing which shows the sample produced in the Example. FIG. 4 shows the transmittance of the laminate of the pressure-sensitive adhesive layer containing the absorbing compound and the hard coat layer, the reflectance of the semi-transparent semi-reflective film alone at an incident angle of 5 °, and the incidence of the optical laminate of the example. It is the figure which showed the reflectance in angle 5 degrees. FIG. 5 is a diagram showing the measurement results of the reflectance with respect to incident light from 5 °, 25 °, and 45 ° of the optical layered body of the example. FIG. 6 is a diagram showing the measurement result of the light emission luminance at 0 ° of the organic EL display device having the optical layered body of the example and the comparative example. FIG. 7 is a diagram showing the measurement result of the light emission luminance at 20 ° of the organic EL display device having the optical layered body of Examples and Comparative Examples. FIG. 8 is a diagram showing the measurement result of the light emission luminance at 40 ° of the organic EL display device having the optical laminates of the example and the comparative example.

In the following description, the description of “A to B” representing a numerical range represents a numerical range including end points. That is, “A or more and B or less” (when A <B) or “A or less and B or more” (when A> B) is represented. Moreover, in the following description, the combination of a preferable aspect is a more preferable aspect.
Embodiments of the present invention will be described below.
[Optical laminate]
The optical layered body of the present invention is an optical layered body having a transflective semi-reflective film, a retardation plate, and a polarizer, and the optical layered body contains a compound having absorption at 480 nm or less, The reflective film has a selective reflection wavelength in a range of 380 nm to 480 nm.
In an image display device, particularly an organic EL display device, blue (B) has the shortest life among red (R), green (G), and blue (B), and a long blue life is desired.
In addition, the present inventors have a large tendency of blue shift in an image display device, particularly an organic EL display device, in a large-screen display device having a large observation angle or a mobile display device when viewed from an oblique direction. I found.
In particular, in a display device having a microcavity structure, the tendency of image blue shift is remarkable. The microcavity structure emphasizes the peak intensity of the emission spectrum by utilizing the resonance effect of light between the upper and lower electrodes of an organic electroluminescence element (hereinafter referred to as organic EL element). By adjusting the optical path length between the upper and lower electrodes of the organic EL element to the emission peak wavelengths of red (R), green (G) and blue (B) of the EL display element, It is a structure in which reflection is repeated and only the light with the matching optical path length is resonated to emphasize. In such a microcavity structure, it is known that the wavelength of the light to be resonated (resonance wavelength) also changes depending on the viewing angle with respect to the organic EL element, and when the viewing angle is large, that is, an organic EL display device or the like. When the display screen is viewed from an oblique direction, there is a problem that the resonance wavelength is shifted to the short wavelength side (blue shift) and cannot be observed with the original color of the organic EL element.

As a result of intensive studies, the present inventors have determined that in an optical laminate including a transflective film, the optical laminate contains a compound having absorption at 480 nm or less, and the transflective film is It has been found that by having a selective reflection wavelength in the range of 380 nm to 480 nm, it is possible to increase the blue light emission luminance at the time of frontal observation and to suppress the blue shift in the observation from an oblique direction.
Although the detailed mechanism by which the above effect is obtained is unknown, a part is considered as follows.
When the optical laminate has a semi-transmissive / semi-reflective film having a selective reflection wavelength of 380 nm or more and 430 nm or less, emitted light in the blue region is increased during front observation, and as a result, blue luminance is improved.
On the other hand, in the observation from the oblique direction, the reflected light is shifted to the shorter wavelength side than the blue region, and thus the blue luminance improvement effect as described above is low. Moreover, since the optical laminated body of this invention contains the compound which absorbs the light of the shifted wavelength range, it is thought that the blue shift of an image is suppressed. Furthermore, in the observation from the oblique direction, the optical distance of the layer containing the compound having absorption at 480 nm or less is longer than that in the front view, so that the absorption is increased according to Lambert Beer's law. It is thought that it contributes to the suppression of the blue shift when observed from an oblique direction.
Hereinafter, the present invention will be described in detail.

<Layer structure of optical laminate>
The optical layered body of the present invention is preferably the following first embodiment or second embodiment. Among these, the first embodiment is more preferable from the viewpoint of easy design of the selective reflection wavelength.
First Embodiment: The semi-transmissive and semi-reflective film is a liquid crystal layer having a cholesteric structure (hereinafter also referred to as “CLC layer”), and the CLC layer, the retardation film, and the polarizer are laminated in this order. .
Second Embodiment: The semi-transmissive / semi-reflective film is a reflective polarizing layer (hereinafter also referred to as “DBEF layer”) that transmits only one of p-wave or s-wave light and reflects the other. A retardation layer, a DBEF layer, and a polarizer are laminated in this order.

  FIG. 1 is a schematic cross-sectional view showing a first embodiment of the optical layered body of the present invention. In FIG. 1, the optical layered body 10 includes a phase difference plate 14 that imparts a phase difference corresponding to ¼ wavelength to transmitted light, and a polarizer 16. The polarizer 16 is a linear polarizer, and the retardation plate 14 and the polarizer 16 constitute a circularly polarizing plate 18. In addition, the CLC layer 12 is provided on the surface of the retardation plate 14 opposite to the side where the polarizer 16 is provided. In the following description, “upper or upper” means the upper side of the figure, and in FIG. 1, the side where the polarizer 16 is provided, and “lower or lower” means that the CLC layer 12 is provided. On the side. Therefore, for example, in FIG. 1, the lower side of the CLC layer means the opposite side of the CLC layer 12 from which the phase difference plate 14 is provided.

Although not shown in FIG. 1, a protective layer (not shown) may be provided above or below the polarizer 16. The protective layer may be composed of only one layer or may be composed of two or more layers, and is not particularly limited, but at least the protective layer of the polarizer 16 such as TAC, the hard coat layer, and the antireflection layer And at least one layer selected from: Further, a hard coat layer or a protective layer may be provided below the CLC layer 12.
In the case of the optical laminated body 10 shown in FIG. 1, the angle formed by the slow axis of the retardation plate 14 and the absorption axis of the polarizer 16 is preferably 45 ± 5 °, and preferably 45 ± 2 °. Is more preferable.
In the present invention, in addition to the above-described retardation plate, polarizer and protective layer, an adhesive layer may be further provided, which is opposite to the side of the retardation plate 14 on which the polarizer 16 is provided. May be provided on the side, may be provided between the polarizer 16 and a protective layer (not shown), or may be provided between two or more protective layers. . Further, it may be provided below the CLC layer 12.
Moreover, the optical laminated body of the 1st embodiment of this invention may have the protective layer formed, for example by TAC between the phase difference plate 14 and the polarizer 16, and is not specifically limited.

In the first embodiment shown in FIG. 1, a display element is disposed below the CLC layer 12. When the display element is an organic electroluminescence display element (hereinafter also referred to as “organic EL display element”), the organic EL display element has a reflective film.
Of the light emitted from the display element, only one of the right circularly polarized light and the left circularly polarized light is transmitted by the CLC layer 12 and the other is reflected and returned downward.
Here, if the CLC layer 12 transmits right circular polarized light and reflects left circular polarized light, the right circular polarized light transmitted through the CLC layer 12 is emitted from the polarizer 16 side. The circularly polarizing plate 18 composed of the polarizer 16 and the retardation plate 14 is designed so that right-handed circularly polarized light is transmitted in accordance with the CLC layer 12. The left circularly polarized light reflected by the CLC layer 12 is reflected by the reflective film of the organic EL display element, becomes right circularly polarized light, and enters the CLC layer 12 again. Since the CLC layer 12 transmits the right circularly polarized light, the right circularly polarized light reflected by the reflective film passes through the CLC layer 12 and is emitted from the polarizer 16 side.
That is, the CLC layer 12 reflects the right circularly polarized light with respect to incident light from below, and the circularly polarizing plate constituted by the phase difference plate and the polarizer transmits the left circularly polarized light, or the CLC layer. Are preferably configured to reflect left circularly polarized light with respect to incident light from below, and the circularly polarizing plate transmits right circularly polarized light.
Therefore, when the CLC layer 12 is not provided, the left circularly polarized light is cut by the circularly polarizing plate 18 and only the right circularly polarized light is transmitted. However, by providing the CLC layer 12, the left circularly polarized light is transmitted by the CLC layer 12. The polarized light is reflected, becomes right circularly polarized light by the reflective film provided under the organic EL display element, and is incident on the optical laminated body 10 again, and is transmitted through the optical laminated body 10. Therefore, the light of a part of the wavelengths reflected by the CLC layer 12 increases the total amount of emitted light. Since the CLC layer 12 reflects right circularly polarized light or left circularly polarized light in a wavelength-dependent manner, the amount of emitted light increases only in the wavelength region.

FIG. 2 is a schematic cross-sectional view showing a second embodiment of the optical layered body of the present invention. In FIG. 2, the optical layered body 20 includes a phase difference plate 24 that imparts a phase difference corresponding to ¼ wavelength to transmitted light, and a polarizer 26. A DBEF layer 22 is provided between the phase difference plate 24 and the polarizer 26.
Although not shown in FIG. 2, a protective layer (not shown) may be provided above or below the polarizer 26. The protective layer may be composed of only one layer or may be composed of two or more layers, and is not particularly limited, but includes at least a protective layer of a polarizer such as TAC, a hard coat layer, and an antireflection layer. It is preferable to have at least one layer selected. Further, a hard coat layer or a protective layer may be provided below the DBEF layer 22 or the retardation film 24.
In the case of the optical laminated body shown in FIG. 2, the angle formed by the slow axis of the phase difference plate 24 and the absorption axis of the polarizer 26 is preferably 45 ± 5 °, and preferably 45 ± 2 °. More preferred.
In the present invention, an adhesive layer may be provided in addition to the above-described retardation plate 24, polarizer 26 and protective layer, and the adhesive layer is provided between the retardation plate 24 and the DBEF layer 22. Alternatively, it may be provided between the polarizer 26 and the DBEF layer 22, or may be provided between the polarizer 26 and a protective layer (not shown). It may be provided between the protective layers. Further, it may be provided below the phase difference plate 24.
Moreover, the optical layered body of the second embodiment of the present invention may have a protective layer formed of TAC or a hard coat layer between the retardation plate 24 and the DBEF layer 22, There is no particular limitation.

In the second embodiment shown in FIG. 2, a display element is disposed below the phase difference plate 24. When the display element is an organic electroluminescence display element (hereinafter also referred to as “organic EL display element”), the organic EL display element has a reflective film.
In FIG. 2, for example, the polarizer 26 and the DBEF layer 22 transmit a p-wave. The polarizer 26 absorbs s waves, and the DBEF layer 22 reflects s waves of some wavelengths. The non-polarized light emitted from the display element passes through the phase difference plate 24, the p-wave is transmitted through the DBEF layer 22, and the s-wave of some wavelengths is reflected. The p-wave transmitted through the DBEF layer 22 is transmitted through the polarizer 26 and emitted.
On the other hand, the s-wave reflected by the DBEF layer 22 passes through the phase difference plate 24 and becomes circularly polarized light. The circularly polarized light is reflected by the reflective film of the organic EL display element, and the direction of the circularly polarized light is reversed. The circularly polarized light reflected by the reflective film is transmitted through the phase difference plate 24 to become a p-wave and transmitted through the DBEF layer 22.
Further, when the reflective layer is not a polarization preserving reflector, or when the polarizing plate 26 gives elliptically polarized light, the s-waves of some wavelengths reflected by the DBEF layer 22 pass through the phase difference plate 24. The s wave reflected by the DBEF layer 22 becomes elliptically polarized light and is reflected by the reflective film of the organic EL display device, and the direction of elliptically polarized light is reversed. Since the elliptically polarized light is a mixture of s wave and p wave, the p wave is transmitted through the DBEF layer 22 and the s wave of some wavelengths is reflected. In the present embodiment, the above reflection and transmission are repeated. In this embodiment, the emitted light is the sum of the p waves emitted at the nth time.
In the case where the DBEF layer is not provided, only the p-wave is transmitted among the light emitted from the display element. However, by providing the DBEF layer, the s-waves of some wavelengths reflected by the DBEF layer are transmitted. Since it is reflected and transmitted as a p-wave, the total amount of emitted light increases.

In addition, in the optical laminated body of this invention, it is preferable that a phase difference plate and an optical laminated body are either of the following (1)-(5).
(1) The retardation plate is a laminate of a positive dispersion λ / 2 retardation plate and a positive dispersion λ / 4 retardation plate, and has a polarizer on the λ / 2 retardation plate side.
(2) The retardation plate has a positive dispersion C positive plate in addition to a positive dispersion λ / 2 retardation plate and a positive dispersion λ / 4 retardation plate. In addition, a polarizer is provided on the λ / 2 retardation plate side. The position of the positive C plate may be between the λ / 2 phase difference plate and the polarizer, or may be on the opposite side of the λ / 4 phase difference plate where the λ / 2 phase difference plate is provided. Not.
(3) The retardation plate is a reverse dispersion λ / 4 retardation plate.
(4) The retardation plate is a laminate of a positive dispersion positive C plate and a reverse dispersion λ / 4 retardation plate. It is preferable to have a polarizer on the λ / 4 retardation plate side.
(5) The retardation plate is a laminate of a reverse dispersion positive C plate and a reverse dispersion λ / 4 retardation plate. It is preferable to have a polarizer on the λ / 4 retardation plate side.
Among these, (2), (4) or (5) is preferable, and (5) is more preferable from the viewpoint of the viewing angle compensation effect.
In the second embodiment of the present invention, a DBEF layer is provided between the retardation plate and the polarizer.

When the optical laminate of the present invention has only a λ / 4 retardation plate as a retardation plate, the λ / 4 retardation plate is preferably a reverse dispersion λ / 4 retardation plate. When the λ / 4 retardation plate has positive dispersion (positive wavelength dispersion characteristic) or flat dispersion (flat wavelength dispersion characteristic), the λ / 4 retardation plate incident from the outside (viewer side) The transmitted light is transmitted to the display element side as elliptically polarized light having an ellipticity different depending on the wavelength. In addition, the light returned from the display element side is also given a phase difference having a wavelength conversion amount depending on the wavelength when passing through the λ / 4 phase difference plate and moving toward the viewer side. The light is emitted from the λ / 4 retardation plate by circularly polarized light or linearly polarized light having different ellipticities. Thereby, the color shift of the return light is more remarkable. On the other hand, when a reverse dispersion λ / 4 retardation plate is used, the entire structure is larger than when a positive dispersion λ / 4 retardation plate and a flat dispersion λ / 4 retardation plate are used. As a result, changes due to wavelength are suppressed.
Here, α (ratio of retardation value (Re450) at a wavelength of 450 nm to retardation value (Re550) at a wavelength of 550 nm (Re450 / Re550)) of the λ / 4 retardation plate is preferably 0.95 or less, more preferably. Is 0.93 or less, more preferably 0.91 or less, and still more preferably 0.89 or less. Further, Re450 / Re550 is preferably 0.78 or more, more preferably 0.80 or more, and further preferably 0.82 or more.
It is preferable that α is in the above-mentioned range since a state close to λ / 4 is maintained in the visible region. α is obtained by measuring a retardation value at a wavelength of 450 nm and a retardation value at a wavelength of 550 nm with a phase difference measuring instrument, and serves as an index of wavelength dispersion.

In addition, when a λ / 4 retardation plate and a λ / 2 retardation plate are used as the retardation plate, it is preferable to arrange the λ / 2 retardation plate on the polarizer side.
When a λ / 4 phase difference layer and a λ / 2 phase difference layer are used as the phase difference layer, the angle formed by the orientation axis of each phase difference layer and the absorption axis of the polarizer is the following (i) or (ii) A range is preferred.
(I) As a first example, the angle formed by the slow axis of the λ / 2 retardation layer and the absorption axis of the polarizer is preferably 15 ± 8 °, more preferably 15 ± 6 °. preferable. At this time, the angle formed by the slow axis of the λ / 4 retardation layer and the absorption axis of the polarizer is preferably 75 ± 15 °, and more preferably 75 ± 13 °.
(Ii) As a second example, the angle formed by the slow axis of the λ / 2 retardation layer and the absorption axis of the polarizer is preferably 75 ± 15 °, more preferably 75 ± 13 °. preferable. At this time, the angle formed by the slow axis of the λ / 4 retardation layer and the absorption axis of the polarizer is preferably 15 ± 8 °, and more preferably 15 ± 6 °.

Here, the in-plane retardation (in-plane retardation value, Re) and the thickness direction retardation (thickness direction retardation value, Rth) are the in-plane refractive index in the slow axis direction nx, and in-plane Where ny is the refractive index in the direction orthogonal to nx, nz is the refractive index in the direction orthogonal to nx and ny, and d is the film thickness.
In-plane retardation (Re) = (nx−ny) × d
Thickness direction retardation (Rth) = ((nx + ny) / 2−nz) × d

  When the optical layered body of the present invention contains a compound having absorption at 480 nm or less in the semi-transmissive / semi-reflective film or any layer on the display element side of the semi-transmissive / semi-reflective film, The average reflectance of light at 530 to 680 nm of the light incident from the side where is disposed is preferably 15% or less, more preferably 12% or less, and even more preferably 10% or less. Although a minimum is not specifically limited, From a viewpoint of manufacturability, Preferably it is 3% or more, More preferably, it is 5% or more. The reflectance is a reflectance at an incident angle of 5 °.

The light reflectance of the optical laminate of the present invention is obtained according to the CIE 1931 standard color system luminous reflectance Y value. Measure the reflectance at each wavelength by entering the light of each wavelength with the opposite side (side on which the display element is arranged) as the incident light side of the retardation layer of the optical laminate. To do. That is, in the first embodiment, the CLC layer side is the incident light side, and in the second embodiment, the phase difference plate side is the incident light side. A black plate is disposed on the polarizer side.
Moreover, the reflectance of light means the average value of the measured value of 16 places, for example, can be calculated | required by the method as described in an Example. In this specification, 16 measurement points are intersection points when a line that divides the vertical direction and the horizontal direction into 5 equal parts is drawn with respect to the area inside the margin, with the area 1 cm from the outer edge of the measurement sample as the margin. It is preferable to set the 16 points of measurement as the center of measurement. When the measurement sample is a quadrangle, measurement is performed centering on 16 intersections of lines obtained by dividing a region 1 cm from the outer edge of the quadrangle as a blank and dividing the region inside the blank into five equal parts in the vertical and horizontal directions. The average value is preferably calculated. When the measurement sample has a shape other than a quadrangle such as a circle, an ellipse, a triangle, or a pentagon, a rectangle with the maximum area inscribed in these shapes can be written, and 16 points can be measured with respect to the rectangle by the above method. preferable.

In the present invention, “average reflectance of light at 530 to 680 nm” is a value obtained by measuring the reflectance every 1 nm or 2 nm in a wavelength range of 530 nm to 680 nm and calculating an average value thereof. Is preferred.
The spectral reflectance of the SCI method is preferably measured every 1 nm or every 2 nm. However, when the measurement wavelength interval of the measuring device exceeds 2 nm, the absolute value of the change in reflectance every 1 nm within the measurement interval is It is preferable to calculate the average of the reflectance as being uniform.

The optical layered body of the present invention contains a compound having absorption at 480 nm or less in a semi-transmissive / semi-reflective film, or when any layer on the display element side of the semi-transmissive / semi-reflective film contains a front surface ( When the half value width of the reflectance peak at 400 to 480 nm measured at an angle of 5 ° is X nm, and the half width of the reflectance peak at 400 to 480 nm measured at an angle (angle 25 °) is Y nm, X> Y is preferred.
Here, the half width described above is based on the reflectance (b%) based on the average reflectance of wavelengths of 500 nm or more and 580 nm or less, and the reflectance of the peak top at 400 to 480 nm (a%) is {b + It is calculated with a width of (a−b) × 0.5}%.
The greater the angle of light incident by the semi-transmissive / semi-reflective film, the more the reflected light shifts to the short wavelength side. In the present invention, since a compound having an absorption at 480 nm or less (hereinafter also referred to as an absorbing compound) is contained, reflected light shifted to the short wavelength side is absorbed by the absorbing compound, and the reflectance at an incident angle of 5 ° is increased. It is considered that the half width of the reflectance at an incident angle of 25 ° is smaller than the half width.
XY is preferably 5 nm or more, more preferably 7 nm or more.

In the optical laminate of the present invention, the reflection wavelength peak of the optical laminate, that is, the optical laminate of the present invention was used for the display panel with respect to the selective reflection center wavelength of the semi-transmissive and semi-reflective film in a region of 480 nm or less. In this case, it is preferable that the peak wavelength at which the luminance is improved is located on the long wavelength side. It is more preferable that the above relationship is satisfied when the transflective film is a CLC layer. Here, the reflection wavelength peak of the optical layered body is a peak wavelength at which the luminance is improved in a region of 480 nm or less when the display device is provided by providing the optical layered body of the present invention. The reflection wavelength peak is measured at an incident angle of 5 °.
When the reflection wavelength peak of the optical laminate is located on the long wavelength side with respect to the selective reflection center wavelength of the semi-transmissive / semi-reflective film, the reflected light is directed to the shorter wavelength side for light incident from an oblique direction. By shifting, since the shifted reflected light is absorbed by the absorbing compound, the occurrence of blue shift when observed from an oblique direction is suppressed, which is preferable.
By designing the selective reflection center wavelength of the semi-transmissive / semi-reflective film to a wavelength region where the absorbing compound absorbs, an optical laminate satisfying the above relationship can be obtained.

In the present invention, when the compound having absorption at 480 nm or less is contained in the transflective film or in any layer on the display element side of the transflective film, the reflection peak of the optical laminate is obtained. Is preferably smaller than the half-value width of the reflection peak of the semi-transmissive semi-reflective film alone. In addition, when a semi-transmissive semi-reflective film is a CLC layer, it is more preferable to satisfy the above relationship. The reflection peak half width is the half width of the reflection peak in reflectance measurement at an incident angle of 5 °.
Here, the above-mentioned half width is the reflectance (b%) based on the average reflectance of wavelengths of 500 nm or more and 580 nm or less, and the reflectance of the peak top from 380 to 480 nm (a%) is {b + It is calculated with a width of (a−b) × 0.5}%.
A part of the short wavelength region of the reflection peak of the semi-transparent semi-reflective film alone is absorbed by the absorbing compound, so that the half-value width of the reflection peak of the optical laminate is reduced to that of the semi-transmissive semi-reflective film alone. It can be made smaller than the half width.
By adopting an optical layered body that satisfies the above-mentioned relationship, for light incident from an oblique direction, the reflected light is shifted to the shorter wavelength side, and the shifted reflected light is absorbed by the absorbing compound. This is preferable because the occurrence of blue shift when observed from above is suppressed.

<Phase difference plate>
The optical layered body of the present invention has a retardation plate.
The retardation plate is a half-wave retardation plate (hereinafter also referred to as “λ / 2 retardation plate”) and a quarter-wave retardation plate (hereinafter also referred to as “λ / 4 retardation plate”). , And combinations thereof. In the present invention, it is preferable to provide at least a λ / 4 retardation plate as the retardation plate. In the present invention, the retardation plate is preferably a λ / 4 retardation plate or a laminate of a λ / 4 retardation plate and a λ / 2 retardation plate, and more preferably a λ / 4 retardation. A plate is more preferable, and a reverse dispersion λ / 4 phase difference plate is still more preferable.
The in-plane retardation at the wavelength of 550 nm is preferably 200 to 300 nm, more preferably 220 to 280 nm, and further preferably 220 to 270 nm.
The in-plane retardation of the λ / 4 retardation plate at a wavelength of 550 nm is preferably 100 to 180 nm, more preferably 110 to 160 nm, and still more preferably 110 to 150 nm.

  The retardation plate of the present invention may further include a positive C plate having a positive C characteristic. The positive C characteristic means that the refractive index in the X-axis direction along the layer surface is nx, the refractive index in the Y-axis direction perpendicular to the X-axis in the direction along the layer surface is ny, and the refractive index in the layer thickness direction is nz. , Nz> nx≈ny, and the optical axis is in the z direction.

The phase difference plate may exhibit normal dispersion wavelength dispersion (hereinafter also referred to as “normal dispersion”) or reverse dispersion wavelength dispersion (hereinafter referred to as “reverse dispersion”). ).
The reverse dispersion is a characteristic that the phase difference given to the transmitted light increases as the wavelength of the transmitted light becomes longer. Specifically, the retardation at a wavelength of 450 nm (Re450) and the retardation at a wavelength of 550 nm (Re550). Is a characteristic of Re450 <Re550. On the other hand, the positive dispersibility is a characteristic that satisfies Re450> Re550.
The thickness of the retardation plate can be appropriately adjusted in the range of 0.1 to 10 μm in consideration of the phase difference to be applied.

The retardation plate used in the present invention may consist of a retardation support having the desired λ / 4 or λ / 2 function by itself, or a support made of a polymer film (transparent support). It may have a retardation layer on it or may be composed of a retardation layer alone. When the retardation layer is composed of a single layer, a desired λ / 4 function or λ / 2 function may be provided by laminating another layer on a support that does not optically affect the layer. The constituent material of the retardation layer is not particularly limited, and both the retardation layer formed from the composition containing the liquid crystal compound and the retardation layer obtained by stretching the polymer film have both layers. You may do it.
Among these, it is preferable that a phase difference plate is a laminated body of a transparent support body and a phase difference layer.

(Transparent support)
In the present invention, the material for the transparent support is not particularly limited. 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; Polyether ether ketone polymer; polyphenylene sulfide polymer; vinylidene chloride polymer; vinyl alcohol polymer; vinyl butyral polymer; arylate polymer; polyoxymethylene polymer; epoxy polymer; The support may be prepared using one or more polymers.

When the retardation film is a laminate of a polymer film (transparent support) and a retardation layer, a laminate of the polymer film (transparent support) and a retardation layer formed from a composition containing a liquid crystalline compound Is preferred. A polymer film having small optical anisotropy may be used, or a polymer film exhibiting optical anisotropy by stretching treatment or the like may be used. The support preferably has a light transmittance of 80% or more.
The thickness of the transparent support is preferably 10 μm to 200 μm, more preferably 10 to 80 μm, and still more preferably 20 to 60 μm.

(Liquid crystal compound)
There is no particular limitation on the type of liquid crystalline compound used for forming the retardation layer. For example, a low-molecular liquid crystalline compound is formed in a nematic alignment in a liquid crystal state, and then a retardation layer obtained by fixing by photocrosslinking or thermal crosslinking, or a high molecular liquid crystalline compound is formed in a nematic alignment in a liquid crystal state and then cooled. Thus, a retardation layer obtained by fixing the orientation may be used. In the present invention, even when a liquid crystalline compound is used in the retardation layer, the retardation layer is a layer formed by fixing the liquid crystalline compound by polymerization or the like. It is not necessary to show liquid crystallinity. The polymerizable liquid crystalline compound may be a polyfunctional polymerizable liquid crystalline compound or a monofunctional polymerizable liquid crystalline compound. The liquid crystalline compound may be a discotic liquid crystalline compound or a rod-shaped liquid crystalline compound.

In the retardation layer, the liquid crystalline compound is preferably fixed in any of the alignment states of vertical blending, horizontal alignment, hybrid alignment, and tilt alignment. From the viewpoint that the viewing angle dependency can be symmetric, the disc surface of the discotic liquid crystalline compound is substantially perpendicular to the film surface (retardation layer surface), or the long axis of the rod-like liquid crystalline compound is the film surface. It is preferably substantially horizontal with respect to (retardation layer surface).
The term “substantially perpendicular to the discotic liquid crystalline compound” means that the average value of the angle between the film surface (retardation layer surface) and the disc surface of the discotic liquid crystalline compound is in the range of 70 ° to 90 °. . The range is preferably 80 ° to 90 °, more preferably 85 ° to 90 °.
The rod-like liquid crystalline compound being substantially horizontal means that the angle formed by the film surface (retardation surface) and the director of the rod-like liquid crystalline compound is in the range of 0 ° to 20 °. The range is preferably 0 ° to 10 °, more preferably 0 ° to 5 °.

  When the retardation plate includes a retardation layer containing a liquid crystalline compound, the retardation layer may be composed of only one layer, or may be a laminate of two or more retardation layers.

  The retardation layer containing a liquid crystal compound is a liquid crystal compound such as a rod-like liquid crystal compound or a discotic liquid crystal compound, and a coating liquid containing a polymerization initiator, an alignment controller, and other additives as described below, if desired. It can form by apply | coating on a transparent support body. It is preferable to form an retardation film by forming an alignment film on the transparent support and coating the coating liquid on the surface of the alignment film. The thickness of the retardation layer is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm, and still more preferably 1 to 5 μm.

-Discotic liquid crystalline compounds-
In the present invention, it is preferable to use a discotic liquid crystalline compound for forming the retardation layer. Discotic liquid crystalline compounds are disclosed in various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); edited by The Chemical Society of Japan, Quarterly Chemical Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhang et al., J Am. Chem. Soc., Vol. 116, page 2655 (1994), etc.). The polymerization of discotic liquid crystalline compounds is described in JP-A-8-27284.

The discotic liquid crystalline compound preferably has a polymerizable group so that it can be fixed by polymerization. For example, a structure in which a polymerizable group is bonded as a substituent to a discotic core of a discotic liquid crystalline compound is conceivable. However, when a polymerizable group is directly connected to the discotic core, the alignment state can be maintained in the polymerization reaction. It becomes difficult. Therefore, a structure having a linking group between the discotic core and the polymerizable group is preferable. That is, the discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following formula.
D (-LP) _n
In the formula, D is a discotic core, L is a divalent linking group, P is a polymerizable group, and n is an integer of 1 to 12. Preferred specific examples of the discotic core (D), the divalent linking group (L) and the polymerizable group (P) in the above formula are (D1) to (D15) described in JP-A No. 2001-4837, respectively. ), (L1) to (L25), and (P1) to (P18), and the contents described in the publication can be preferably used. In addition, the discotic nematic liquid crystal phase-solid phase transition temperature of the liquid crystalline compound is preferably 30 to 300 ° C, and more preferably 30 to 170 ° C.

-Rod-like liquid crystalline compound-
In the present invention, a rod-like liquid crystalline compound may be used for forming the retardation layer of the retardation plate. Examples of rod-like liquid crystalline compounds 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 exemplified. Not only the above low-molecular liquid crystalline compounds but also high-molecular liquid crystalline compounds can be used. More preferably, the orientation of the rod-like liquid crystalline compound is fixed by polymerization. The liquid crystalline compound preferably has a partial structure capable of causing polymerization or a crosslinking reaction by actinic rays, electron beams, heat, or the like, and more preferably has a polymerizable group.
The number of the partial structures is preferably 1 to 6, more preferably 1 to 3. As the polymerizable rod-like liquid crystalline compound, Makromol. Chem. 190, 2255 (1989), Advanced Materials, 5, 107 (1993), U.S. Pat. Nos. 4,683,327, 5,622,648, 5770107, International Publication WO95 / 22586. Gazette, 95/24455 gazette, 97/00600 gazette, 98/23580 gazette, 98/52905 gazette, JP-A-1-272551 gazette, 6-166616 gazette, 7-110469 gazette. The compounds described in JP-A No. 11-80081, JP-A No. 2001-328773 and the like can be used.
Specific examples of the rod-like liquid crystalline compound include compounds represented by the following formulas (1) to (17).

  In addition, examples of the liquid crystalline compound exhibiting reverse dispersibility include JP 2010-537954 A, JP 2010-537955 A, JP 2010-522892 A, JP 2010-522893 A, and JP 2013-2013. Examples thereof include compounds described in each published gazette such as 509458 gazette and patent gazettes such as Japanese Patent No. 5892158, Japanese Patent No. 5979136, Japanese Patent No. 5994777, and Japanese Patent No. 6015655.

  A liquid crystal compound can be used individually by 1 type or in combination of 2 or more types. In the case of one kind alone, the one kind of liquid crystalline compound is preferably a polymerizable liquid crystalline compound. Moreover, when using 2 or more types in combination, it is preferable that at least 1 type is a polymeric liquid crystalline compound, and it is more preferable that all are polymeric liquid crystalline compounds.

(Polymerization initiator)
The aligned liquid crystal compound is fixed while maintaining the alignment state. The fixing preferably uses a polymerization reaction, and the polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. Among these, a photopolymerization reaction is preferable. Examples of photopolymerization initiators include α-carbonyl compounds (see US Pat. Nos. 2,367,661 and 2,367,670), acyloin ethers (see US Pat. No. 2,448,828), α-hydrocarbon substituted aromatics. Group acyloin compounds (see US Pat. No. 2,722,512), polynuclear quinone compounds (see US Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketone (US patents) No. 3549367), acridine and phenazine compounds (see JP-A-60-105667, US Pat. No. 4,239,850) and oxadiazole compounds (see US Pat. No. 4,221,970).

It is preferable that the usage-amount of a polymerization initiator is 0.01-20 mass% with respect to the total solid of the composition for phase difference layer formation, and it is more preferable that it is 0.5-5 mass%. Light irradiation for the polymerization of the liquid crystalline compound is preferably performed using ultraviolet rays. The irradiation energy is preferably ^{20mJ / cm 2 ~50J / cm 2} , more preferably at 100 to 800 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.

(Surfactant)
The composition for forming a retardation layer preferably contains a surfactant. Among the surfactants, it is preferable to select and use one or more selected from a fluorine-based surfactant having a polymerizable group and a silicon-based surfactant having a polymerizable group.
The content of the surfactant is preferably 0.01 to 2.0% by mass, and preferably 0.1 to 1.0% by mass with respect to the total solid content of the composition for forming a retardation layer. More preferred.

(solvent)
The composition for forming a retardation layer usually contains a solvent.
Solvents include ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, N-methyl-2-pyrrolidone, etc.), ethers (dioxane, tetrahydrofuran, etc.), aliphatic hydrocarbons (hexane, etc.), Alicyclic hydrocarbons (cyclohexane, etc.), aromatic hydrocarbons (toluene, xylene, etc.), halogenated carbons (dichloromethane, dichloroethane, etc.), esters (methyl acetate, ethyl acetate, butyl acetate, etc.), alcohols (Butanol, cyclohexanol, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.), cellosolve acetates, sulfoxides (dimethylsulfoxide, etc.), amides (dimethylformamide, dimethylacetamide, etc.), etc., and mixtures thereof It may be.

  The retardation layer can be formed, for example, by applying, drying, and curing a retardation layer forming composition. Moreover, it is preferable to apply | coat the composition for phase difference layer formation on alignment film.

(Vertical alignment accelerator)
When forming the retardation layer, in order to uniformly align the molecules of the liquid crystalline compound vertically, an alignment control agent capable of vertically controlling the liquid crystalline compound on the alignment film interface side and the air interface side is used. Is preferred. For this purpose, a retardation layer is formed by using a composition containing, together with a liquid crystal compound, a compound that acts on the alignment film to vertically align the liquid crystal compound by an excluded volume effect, an electrostatic effect, or a surface energy effect. Is preferably formed. In addition, regarding the orientation control on the air interface side, a compound that is unevenly distributed at the air interface at the time of orientation of the liquid crystalline compound and has an action of vertically aligning the liquid crystalline compound by its excluded volume effect, electrostatic effect, or surface energy effect, It is preferable to form a retardation layer using the composition contained with a liquid crystalline compound. As such a compound (alignment film interface side vertical alignment accelerator) that promotes the vertical alignment of the molecules of the liquid crystalline compound on the alignment film interface side, a pyridinium derivative is preferably used. As a compound (air interface side vertical alignment accelerator) that promotes the vertical alignment of the molecules of the liquid crystal compound on the air interface side, a fluoro aliphatic group that promotes the uneven distribution of the compound on the air interface side and One or more hydrophilic groups selected from the group consisting of carboxy group (—COOH), sulfo group (—SO ₃ H), phosphonoxy group {—OP (═O) (OH) ₂ } and salts thereof. The containing compound is preferably used. Further, by blending these compounds, for example, when a liquid crystalline composition is prepared as a coating solution, the coating property of the coating solution is improved, and the occurrence of unevenness and repellency is suppressed.
Paragraphs 0101 to 0185 of International Publication No. 2013/100115 are referred to as the vertical alignment accelerator.

(Other additives)
In the present invention, the composition for forming a retardation layer may have a plasticizer, a polymerizable monomer and the like in addition to the above components. These components are preferably compatible with the liquid crystal compound and do not inhibit the alignment.
Examples of the polymerizable monomer include radically polymerizable or cationically polymerizable compounds, preferably polyfunctional radically polymerizable monomers, and compounds that are copolymerizable with the above-described polymerizable group-containing liquid crystalline compounds. Examples thereof include the compounds described in paragraphs 0018 to 0020 of JP-A No. 2002-296423. The addition amount of the polymerizable compound is preferably 1 to 50 parts by mass, more preferably 5 to 30 parts by mass with respect to 100 parts by mass of the liquid crystalline compound.

(Method of applying retardation layer)
The composition for forming the retardation layer can be applied by a known method (eg, wire bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).

(Alignment film)
The retardation plate may have an alignment film.
The alignment film has a role of easily aligning the liquid crystalline compound in the retardation layer when the retardation layer forming composition is applied, dried and cured to form the retardation layer.
In addition, even if it has an alignment film at the time of formation of the phase difference layer, if the phase difference layer is transferred to another member and the alignment film is not transferred at the time of transfer, it does not have an alignment film. A laminate can be obtained.

The alignment film can be formed into an alignment layer by, for example, applying an alignment layer forming composition on a transparent substrate and applying an alignment regulating force. The composition for forming an alignment film can be appropriately selected from conventionally known materials such as a photodimerization type material.
The means for imparting alignment regulating force to the alignment film can be a conventionally known one, and examples thereof include a rubbing method, a photo-alignment method, and a shaping method.
The thickness of the alignment film is preferably 1 to 1,000 nm, and more preferably 60 to 300 nm.

<Polarizer>
In the present invention, the optical laminate has a semi-transmissive / semi-reflective film, a retardation plate, and a polarizer. The polarizer preferably forms a polarizing plate together with a protective film.
As the polarizer, any of an iodine-based polarizer, a dye-based polarizer using a dichroic dye, and a polyene-based polarizer may be used.
The iodine polarizer and the dye polarizer are generally produced using a polyvinyl alcohol film. The absorption axis of the polarizer corresponds to the stretching direction of the film. Accordingly, a polarizer stretched in the longitudinal direction (transport direction) has an absorption axis parallel to the longitudinal direction, and a polarizer stretched in the lateral direction (perpendicular to the transport direction) is perpendicular to the longitudinal direction. Has an absorption axis.

In the present invention, the above-described retardation plate and polarizer preferably constitute a circularly polarizing plate or an elliptically polarizing plate. A linear polarizer is used as the polarizer, and the circularly polarizing plate is combined with the above retardation plate. It is more preferable to constitute a functioning polarizer-integrated optical laminate.
The circularly polarizing plate is disposed on an organic electroluminescence display device or a resistive film type touch panel and has a role of exhibiting antireflection ability.
The optical layered body of the present invention includes a retardation plate and a polarizer. However, the retardation plate and the polarizer may be in a film form, and are formed by coating or the like to form a layer. It may be a thing and is not limited to the aspect which forms plate shape independently.
In addition, when applying the optical laminated body of this invention to a display panel or an image display apparatus, it is preferable that the phase difference plate is provided in the light source side.

<Semi-transmissive semi-reflective film>
The transflective film included in the optical layered body of the present invention is preferably either a CLC layer or a DBEF layer.
Here, the “semi-transmissive / semi-reflective film” is a film that transmits predetermined polarized light, reflects other polarized light, and has wavelength dependency of reflected light. The polarized light means circularly polarized light, linearly polarized light, s wave, p wave, and the like. The reflectance can be set as appropriate, and the reflectance is not limited to 50%.
In particular, the semi-transmissive / semi-reflective film preferably has wavelength dependency of light to be reflected, and the wavelength that can be selectively reflected is preferably 480 nm or less, more preferably 460 nm or less, in measurement at an incident angle of 5 °. Preferably it is 440 nm or less. Moreover, although a lower limit is not specifically limited, Preferably it is 380 nm or more, More preferably, it is 400 nm or more, More preferably, it is 415 nm or more. If the selective reflection wavelength has a peak, it is preferable that the selective reflection wavelength has a peak in the above-described wavelength region, but it is not always necessary to have a peak and is not particularly limited as long as selective reflection is possible in the above-described wavelength region. . Note that the transflective film is preferably a transflective film having low reflectivity or no reflectivity in a region exceeding 480 nm.
B / A is preferably 0.5 or less, more preferably 0.3, where A is the maximum reflectance of 380 nm or more and 480 nm or less of the transflective film, and B is the reflectance at 480 nm.
When the selective reflection wavelength is within the above range, when the light reflected by the semi-transmissive / semi-reflective film is emitted with respect to the incident light from the front, it becomes a blue wavelength region, so that the blue emission luminance is improved. be able to. On the other hand, for incident light from an oblique direction, the light reflected by the semi-transmissive / semi-reflective film shifts to the short wavelength side, and the shifted light is absorbed by the absorbing compound, thereby suppressing the occurrence of blue shift. Is done.

(Liquid crystal layer having a cholesteric structure (CLC layer))
The optical layered body of the present invention preferably has a liquid crystal layer (CLC layer) having a cholesteric structure as a transflective film.
In this specification, the CLC layer refers to a layer made of liquid crystalline molecules exhibiting cholesteric regularity. Cholesteric regularity means that the molecular axes are aligned in a certain direction on one plane, but the direction of the molecular axis is slightly shifted in the next plane that overlaps it, and the angle is further shifted in the next plane. In this way, the molecular axes in the planes are shifted (twisted) as they sequentially pass through the overlapping planes. Thus, the structure in which the direction of the molecular axis is twisted becomes a chiral structure.

  A cholesteric liquid crystal layer generally has an optical rotation selection characteristic that separates an optical rotation component in one direction and an optical rotation component in the opposite direction based on a physical molecular arrangement. Light incident on such a liquid crystal layer along the helical axis of the liquid crystal planar array is divided into two circularly polarized light, right-handed and left-handed, one of which is transmitted and the other is reflected. This phenomenon is known as circular dichroism, and when the direction of rotation in the helical structure of liquid crystal molecules is appropriately selected, circularly polarized light having the same optical rotation direction as that of the rotation direction is selectively reflected.

In this case, the maximum optical polarization polarization light reflection occurs at a wavelength λ ₀ of the following formula (1). That is, λ ₀ means the center wavelength of reflected light (selective reflection center wavelength).
λ ₀ = nav · p (1)
Here, p is a helical pitch in the helical structure of liquid crystal molecules, and nav is an average refractive index in a plane perpendicular to the helical axis.
Further, the wavelength bandwidth Δλ of the reflected light at this time is represented by the following formula (2).
Δλ = Δn · p (2)
Here, Δn is the birefringence value of the liquid crystal material.

The polarization separation action of the cholesteric liquid crystal layer alone will be described. If unpolarized light is incident on the cholesteric liquid crystal layer, the light of the right旋又range of the wavelength lambda ₀ the wavelength band width Δλ centered is reflected one circularly polarized light component of the left-handed polarization component and the other the other circle Light in the wavelength range (non-polarized light) is transmitted. The reflected right-handed or left-handed circularly polarized light is reflected as it is without being inverted in phase, unlike normal reflection.

As described above, the selective reflection center wavelength region of the cholesteric liquid crystal layer is preferably 480 nm or less, more preferably 460 nm or less, still more preferably 440 nm or less, and preferably 380 nm or more, when measured at an incident angle of 5 °. More preferably, it is 400 nm or more, More preferably, it is 415 nm or more. By making the selective reflection center wavelength within the above-mentioned range, the luminance of light in the blue region is improved when viewed from the front, and the reflected light is shifted by a short wavelength when viewed from an oblique direction. It is preferable that the compound is absorbed by the absorbing compound because the luminance improvement in the blue region is suppressed and the blue shift is suppressed.
In addition, it is preferable that the reflectance of the cholesteric liquid crystal layer is higher because the amount of light emitted during observation from the front direction increases in the optical laminate of the present invention.

Examples of the cholesteric liquid crystal layer include a cured product of a curable composition containing a liquid crystalline monomer or oligomer having a polymerizable group and a liquid crystal polymer in a glass state.
Among these, the cholesteric liquid crystal layer is preferably a cured product of a curable composition containing a liquid crystalline monomer or oligomer having a polymerizable group. This is because when the cholesteric liquid crystal layer is a cured product of the curable composition, the liquid crystal molecules can be optically fixed in the cholesteric liquid crystal state and the handleability is improved.
The curable composition may be ionizing radiation curable or thermosetting, but is preferably an ionizing radiation curable composition from the viewpoint of filter productivity. In this specification, the ionizing radiation means an electromagnetic wave or charged particle beam having an energy quantum capable of polymerizing or cross-linking molecules, and usually ultraviolet (UV) or electron beam (EB) is used. In addition, electromagnetic waves such as X-rays and γ-rays, and charged particle beams such as α-rays and ion beams can also be used.

Examples of the polymerizable group include an ethylenically unsaturated bond group such as a (meth) acryloyl group, a vinyl group and an allyl group, and an epoxy group and an oxetanyl group. From the viewpoint of polymerizability, a (meth) acryloyl group or a vinyl group is preferable, and a (meth) acryloyl group is more preferable.
From the viewpoint of obtaining a cholesteric liquid crystal layer in which liquid crystal molecules are optically fixed by three-dimensional crosslinking, the liquid crystal monomer or oligomer having a polymerizable group may have at least one polymerizable group. It is preferable to have two or more polymerizable groups, and a bifunctional liquid crystalline monomer or oligomer having a polymerizable group at both ends is more preferable.

  As a liquid crystalline monomer which has a polymeric group, the liquid crystalline monomer currently disclosed by Unexamined-Japanese-Patent No. 7-258638 and Japanese Patent Publication No. 10-508882 is mentioned, for example. Examples of the liquid crystalline oligomer having a polymerizable group include cyclic organopolysiloxane compounds having a cholesteric phase as disclosed in JP-A-57-165480.

  Specific examples of the liquid crystalline monomer having a polymerizable group include a liquid crystalline monomer having an acryloyl group at both ends, represented by the following structural formula (I).

The cholesteric liquid crystal layer is more preferably a cured product of a curable composition containing a liquid crystalline monomer or oligomer having a polymerizable group and a chiral agent. When the liquid crystalline monomer or oligomer is formed into a liquid crystal layer at a predetermined temperature, a nematic state is obtained. However, when a chiral agent is added thereto, a chiral nematic liquid crystal (that is, cholesteric liquid crystal) is obtained. In addition, by changing the chiral power by changing the type of chiral agent used, or by changing the blending amount of the chiral agent, the helical pitch in the helical structure of the liquid crystal molecules contained in the cholesteric liquid crystal layer can be adjusted, Thereby, the selective reflection wavelength region of the cholesteric liquid crystal layer can be adjusted.
The cholesteric liquid crystal layer may be made of discotic liquid crystal. For the cholesteric liquid crystal layer, for example, a chiral discotic compound as described in JP-A-2000-086591 may be used, and JP-A-2000-11734 and JP-A-2000-171537. A copolymer of a non-chiral discotic liquid crystalline compound and a chiral discotic compound having a polymerizable group, as described in JP-A No. 2000-347039 and the like, may be used. By producing the cholesteric liquid crystal layer from discotic liquid crystal, the cholesteric liquid crystal layer also has a function as a positive C plate, so that the positive C plate in the retardation plate can be omitted.

From the viewpoint of obtaining a cholesteric liquid crystal layer in which liquid crystalline molecules are optically fixed by three-dimensional crosslinking, the cholesteric liquid crystal layer includes a liquid crystalline monomer or oligomer having a polymerizable group and a chiral agent having a polymerizable group. More preferably, it is a cured product of the curable composition.
The chiral agent having a polymerizable group is preferably a chiral agent having two or more polymerizable groups from the viewpoint of obtaining a cholesteric liquid crystal layer in which liquid crystalline molecules are optically fixed by three-dimensional crosslinking. It is more preferable that it is a bifunctional chiral agent having a polymerizable group. Examples of the polymerizable group include an ethylenically unsaturated bond group such as a (meth) acryloyl group, a vinyl group and an allyl group, and an epoxy group and an oxetanyl group. From the viewpoint of polymerizability, a (meth) acryloyl group or a vinyl group is preferable, and a (meth) acryloyl group is more preferable.

Examples of the chiral agent include chiral compounds disclosed in JP-A-7-258638 and JP-T-10-508882.
Examples of the commercially available chiral agent include a chiral agent “Pariocolor (registered trademark) LC756” (manufactured by BASF) having an acryloyl group as a polymerizable group at both ends.

  The amount of the chiral agent in the cholesteric liquid crystal layer is not particularly limited as long as the desired wavelength selectivity is obtained, but the liquid crystalline monomer, liquid crystalline oligomer in the curable composition used for forming the cholesteric liquid crystal layer, And as a compounding quantity of a chiral agent when the total amount of a chiral agent is 100 mass parts, it is 0.5-20 mass parts normally, Preferably it is 1-15 mass parts, More preferably, it is 2-10 mass parts.

The curable composition used for forming the cholesteric liquid crystal layer is preferably one that is cured by the irradiation of ionizing radiation described above. When an electron beam is used as the ionizing radiation, the acceleration voltage can be appropriately selected according to the material used and the thickness of the layer, but it is usually preferable to cure at an acceleration voltage of about 70 to 300 kV.
When ultraviolet rays are used as the ionizing radiation, those containing ultraviolet rays having a wavelength of 190 to 380 nm are usually emitted. There is no restriction | limiting in particular as an ultraviolet-ray source, For example, a high pressure mercury lamp, a low pressure mercury lamp, a metal halide lamp, a carbon arc lamp, etc. are used.

The curable composition used for forming the cholesteric liquid crystal layer preferably further contains a photopolymerization initiator. This is because the liquid crystalline monomer or oligomer having a polymerizable group and the chiral agent having a polymerizable group in the curable composition can be cured by ultraviolet irradiation.
Examples of the photopolymerization initiator include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzyldimethyl ketal, benzoylbenzoate, α-acyloxime ester, thioxanthones, and the like.
The said photoinitiator can be used individually by 1 type or in combination of 2 or more types.
The amount of the photopolymerization initiator in the curable composition is 1 to 10 mass as a blending amount of the photopolymerization initiator when the total amount of the liquid crystalline monomer, the liquid crystalline oligomer and the chiral agent is 100 parts by mass. Part is preferable, and 2 to 8 parts by mass is more preferable.

  The curable composition used for forming the cholesteric liquid crystal layer is a photopolymerization accelerator, a lubricant, a plasticizer, a filler, an antistatic agent, an antiblocking agent, a cross-linking agent, and a light stability, as long as the effects of the present invention are not impaired. You may contain other components, such as an agent, a ultraviolet absorber, antioxidant, a electrically conductive agent, a refractive index regulator, and a solvent.

When the material constituting the cholesteric liquid crystal layer is a liquid crystalline polymer, specific examples thereof include a polymer in which a mesogenic group exhibiting liquid crystallinity is introduced into a main chain, a side chain, or a position of the main chain and the side chain, and a cholesteryl group. Examples of the polymer cholesteric liquid crystal introduced into the side chain include a liquid crystalline polymer disclosed in JP-A-9-133810 and a liquid crystalline polymer disclosed in JP-A-11-293252.
As the liquid crystalline polymer, a cholesteric liquid crystalline polymer itself having a chiral ability may be used, or a mixture of a nematic liquid crystalline polymer and a cholesteric liquid crystalline polymer may be used. Such a liquid crystalline polymer changes its state depending on the temperature. For example, when the glass transition temperature is 90 ° C. and the isotropic transition temperature is 200 ° C., it exhibits a cholesteric liquid crystal state between 90 ° C. and 200 ° C. Can be solidified in a glass state with the cholesteric structure.

  When the liquid crystal material constituting the cholesteric liquid crystal layer has a glass transition temperature, such as a liquid crystal polymer, it is possible to perform ON / OFF control of the liquid crystal by changing the temperature. Using this property, the selective transmission filter of the present invention can be temporarily changed to a total transmission or total shielding filter as necessary. Further, it is possible to provide a color change function depending on temperature.

  In order to adjust the selective reflection wavelength range of incident light caused by the cholesteric structure of the liquid crystalline polymer, the chiral power in the liquid crystalline polymer molecule may be adjusted by a known method. When a mixture of nematic liquid crystalline polymer and cholesteric liquid crystalline polymer is used, the mixing ratio is adjusted.

  In the present invention, the cholesteric liquid crystal layer may have a single layer structure composed of only one liquid crystal layer or a multilayer structure in which two or more liquid crystal layers are stacked. By adopting a structure in which two or more cholesteric liquid crystal layers having different helical pitches of liquid crystal molecules are laminated, a filter having a plurality of or a wide selective reflection wavelength region can be obtained.

When the cholesteric liquid crystal layer has a multilayer structure, the number of layers is not particularly limited, but preferably 2 to 6 layers from the viewpoint of productivity, light transmittance, and suppression of disorder of alignment of liquid crystal molecules. More preferably, there are 2 to 4 layers.
The thickness of the cholesteric liquid crystal layer varies depending on the type of liquid crystalline monomer or oligomer used, the type of polymer or chiral agent, and the selective reflection wavelength range of the desired cholesteric liquid crystal layer, but increases the reflectance of incident light. From the viewpoint, it is preferably 0.2 μm or more, more preferably 0.5 μm or more, and further preferably 1 μm or more. Further, from the viewpoint of miniaturization and thinning of various members on which the selective transmission filter of the present invention is mounted, the thickness of the cholesteric liquid crystal layer is preferably 100 μm or less, more preferably 80 μm or less, and still more preferably 50 μm or less. More preferably, it is 30 micrometers or less, More preferably, it is 20 micrometers or less, More preferably, it is 10 micrometers or less. The thickness of the cholesteric liquid crystal layer is the thickness of the entire liquid crystal layer, or the total thickness when the liquid crystal layer is two or more layers.

  The thickness of the cholesteric liquid crystal layer can be calculated, for example, by measuring the thickness of 10 locations from a cross-sectional image taken using a scanning transmission electron microscope (STEM) and calculating the average value of 10 locations. The acceleration voltage of the STEM is preferably 10 kV to 30 kV. The STEM magnification is preferably 1,000 to 7,000 times when the measured film thickness is in the micron order, and preferably 50,000 to 300,000 times when the measured film thickness is in the nano order.

There is no restriction | limiting in particular in the formation method of a cholesteric liquid crystal layer, A well-known method can be used. Hereinafter, the case where the cholesteric liquid crystal layer is a cured product of the ionizing radiation curable composition containing the liquid crystalline monomer or oligomer described above will be described as an example.
First, an ionizing radiation curable composition for forming a cholesteric liquid crystal layer comprising an alignment film formed on a glass substrate and further containing other components such as a liquid crystalline monomer or oligomer, a chiral agent, a photopolymerization initiator, and a solvent. Is applied, and liquid crystalline molecules (liquid crystalline monomers and oligomers) are aligned by the alignment regulating force of the alignment film. Next, the liquid crystalline monomer or oligomer is three-dimensionally cross-linked by irradiating with ionizing radiation in this alignment state to obtain a cholesteric liquid crystal layer that is a cured product of the curable composition.
Examples of the method for applying the curable composition include spin coating, dipping, spraying, die coating, bar coating, roll coater, meniscus coater, flexographic printing, screen printing, and bead coater. And various known methods.
When the said curable composition contains a solvent, after apply | coating this curable composition, it is preferable to dry for 10 to 120 second at 30-120 degreeC, for example.

  The alignment film can be produced by a conventionally known method. For example, a method of forming a polyimide film on a glass substrate and rubbing; a method of forming a polymer compound as a photo-alignment film on a glass substrate and irradiating polarized UV (ultraviolet light); stretched PET (polyethylene terephthalate) Examples include a method using a film; a patterning method using a mask; and the like.

  When the cholesteric liquid crystal layer is composed of the liquid crystalline polymer described above, an alignment film is formed on the glass substrate in the same manner as described above, and the composition containing the liquid crystalline polymer is applied on the alignment film by the above method. The polymer is oriented by the orientation regulating force of the orientation film. A cholesteric liquid crystal layer can be obtained by drying as necessary and then cooling to fix the liquid crystalline polymer in a glassy state.

Even when the cholesteric liquid crystal layer has a multilayer structure, it can be formed by sequentially laminating liquid crystal layers by the same method as described above. The plurality of liquid crystal layers may be directly laminated, or may be laminated via an optical adhesive layer or an arbitrary layer.
When laminating a plurality of liquid crystal layers, it is preferable that the director directions of the liquid crystal molecules in the adjacent cholesteric liquid crystal layers are substantially parallel to each other from the viewpoint of reducing alignment disorder.

In the present invention, the cholesteric liquid crystal layer is also preferably reversely dispersible. By making the cholesteric liquid crystal layer have inverse dispersion, the half width of selective reflection can be reduced. As a result, when displaying a black image during front view, the tendency of the red reflected light to become strong is suppressed, and a higher quality image can be obtained.
A cholesteric liquid crystal layer exhibiting reverse dispersion can be obtained by applying a liquid crystal material exhibiting reverse dispersion wavelength characteristics or a liquid crystal material having a cyclohexane structure.
Examples of the liquid crystal material exhibiting the reverse dispersion include, for example, JP-T-2010-528992, JP-A-2006-243470, JP-A-2007-243470, JP-A-2009-75494, and JP-A-2009-62508. Examples thereof include liquid crystal compounds described in JP-A-2009-179563, JP-A-2009-242717, JP-A-2009-242718, JP-A-4422360, and JP-A-41896981.
Examples of the liquid crystal material having a cyclohexane structure include, for example, JP 2001-163833, JP 2007-91612, JP 2007-91796, JP 2006-241403, JP 2006-70080, JP 2006-37005, JP A material prepared by adding a polymerizable group such as an acrylate group to a molecular terminal of a liquid crystal material described in 2006-8928 or a material described in JP-A-2008-274204 can be applied.

(DBEF layer)
In the present invention, a DBEF layer may be used as the transflective film.
Examples of DBEF include multilayer optical film reflective polarizers, such as the reflective polarizer described in US Pat. No. 5,882,774, DBEF-D2-400 available from 3M Company, Examples are DBEF-D4-400.

The DBEF layer transmits light having a single polarization state and reflects the remaining light. The DBEF layer generally transmits p-wave (also referred to as p-polarized light, which has an electric field oscillating in the incident surface), and reflects s-wave (also referred to as s-polarized light, which is an electric field oscillated perpendicular to the incident surface).
Specifically, the DBEF layer is preferably a multilayer laminate in which layers A having birefringence and layers B having substantially no birefringence are alternately laminated. For example, the total number of layers in such a multilayer stack can be 50 to 1,000. The refractive index nx _{A in} the x-axis direction of the A layer is larger than the refractive index ny _{A in the} y-axis direction (nx _A > ny _A ), and the refractive index nx _B in the x-axis direction and the refractive index ny _{B in the} y-axis direction of the B layer. Is substantially the same (nx _B ≈ny _B ). Therefore, the refractive index difference between the A layer and the B layer is large in the x-axis direction and is substantially zero in the y-axis direction. As a result, the x-axis direction becomes the reflection axis, and the y-axis direction becomes the transmission axis. The difference in refractive index between the A layer and the B layer in the x-axis direction is preferably 0.1 to 0.4, and more preferably 0.2 to 0.3. The x-axis direction corresponds to the extending direction of the DBEF layer in the DBEF layer manufacturing method. When the difference in refractive index between the A layer and the B layer in the x-axis direction is large, the reflectance increases, so that the number of layers can be reduced. On the other hand, in order to increase the difference in refractive index, stronger stretching is required, so material selection and process optimization are necessary, and the bowing phenomenon is likely to occur and productivity is likely to decrease. It is done.

  The A layer is preferably made of a material that exhibits birefringence by stretching. Representative examples of such materials include naphthalene dicarboxylic acid polyesters (for example, polyethylene naphthalate), polycarbonates, and acrylic resins (for example, polymethyl methacrylate). Polyethylene naphthalate is preferred. The B layer is preferably made of a material that does not substantially exhibit birefringence even when stretched. A typical example of such a material is a copolyester of naphthalenedicarboxylic acid and terephthalic acid.

  The DBEF layer completely separates the p-wave and s-wave by repeatedly using a slight difference in reflectance between the p-wave and s-wave at the interface between the A-layer and B-layer to form a multilayer structure. One is transmitted and the other is reflected.

The overall thickness of the DBEF layer can be appropriately set according to the purpose, the total number of layers included in the DBEF layer, and the like. The total thickness of the reflective polarizer is preferably 10 μm to 150 μm.
In one embodiment, in the optical laminate, the DBEF layer is disposed so as to transmit light having a polarization direction parallel to the transmission axis of the polarizer. That is, the DBEF layer is arranged so that the transmission axis thereof is substantially parallel to the transmission axis direction of the polarizer. By setting it as such a structure, the light absorbed by the polarizer can be reused.

  The DBEF layer can typically be made by a combination of coextrusion and transverse stretching. Coextrusion can be performed in any suitable manner. For example, a feed block method or a multi-manifold method may be used. For example, the material constituting the A layer and the material constituting the B layer are extruded in a feed block, and then multilayered using a multiplier. Such a multi-layer apparatus is known to those skilled in the art. Next, the obtained long multilayer laminate is typically stretched in a direction (TD) orthogonal to the transport direction. The material constituting the A layer (for example, polyethylene naphthalate) increases the refractive index only in the stretching direction due to the transverse stretching, and as a result, develops birefringence. The refractive index of the material constituting the B layer (for example, a copolyester of naphthalenedicarboxylic acid and terephthalic acid) does not increase in any direction even by the transverse stretching. As a result, a reflective polarizer having a reflection axis in the stretching direction (TD) and a transmission axis in the transport direction (MD) can be obtained. In addition, extending | stretching operation can be performed using arbitrary appropriate apparatuses.

As described above, the selective reflection center wavelength region of the DBEF layer is preferably 480 nm or less, more preferably 460 nm or less, still more preferably 440 nm or less, and preferably 380 nm or more, as measured at an incident angle of 5 °. More preferably, it is 400 nm or more, More preferably, it is 415 nm or more. By making the selective reflection center wavelength within the above-mentioned range, the luminance of light in the blue region is improved when viewed from the front, and the reflected light is shifted by a short wavelength when viewed from an oblique direction. It is preferable that the compound is absorbed by the absorbing compound because the luminance improvement in the blue region is suppressed and the blue shift is suppressed.
In addition, it is preferable that the DBEF layer has a higher reflectance because the amount of light emitted during observation from the front direction increases in the optical laminate of the present invention.

<Protective layer>
The optical laminate of the present invention preferably has a protective layer laminated directly or indirectly on the surface opposite to the side where the retardation plate of the polarizer is provided.
In the present invention, an antireflection layer described later may be used as a protective layer. When a protective layer is laminated separately from the antireflection layer, it is preferable to use a cellulose ester film having high optical isotropy as the protective layer. Moreover, you may have functional layers, such as a hard-coat layer and a glare-proof layer, as a protective layer.
The protective layer is not limited to this, and may be provided on the surface of the polarizer where the retardation plate is provided, and the retardation plate of the polarizer is provided. It may be provided on the opposite surface and is not particularly limited.

-Antireflection layer-
The optical laminate or display panel of the present invention may have an antireflection layer as a protective layer.
In the simplest configuration, the antireflection layer has a configuration in which only the low refractive index layer is coated on the outermost surface of the film. In order to further reduce the surface reflectance, it is preferable to configure the antireflection layer by combining a high refractive index layer having a high refractive index and a low refractive index layer having a low refractive index. As a configuration example, two layers of a high refractive index layer / low refractive index layer or three layers having different refractive indexes are arranged in order from the bottom, and a medium refractive index layer (having a higher refractive index than the lower layer and a high refractive index). In some cases, a layer having a lower refractive index than a layer) / a layer having a higher refractive index / a layer having a lower refractive index are stacked in this order. Among them, from the viewpoint of durability, optical characteristics, cost, productivity, etc., it is preferable to have a medium refractive index layer / high refractive index layer / low refractive index layer in this order on the hard coat layer, for example, JP-A-8-122504. Examples include the configurations described in JP-A-8-110401, JP-A-10-300902, JP-A 2002-243906, JP-A 2000-11706, and the like. Japanese Patent Application Laid-Open No. 2008-262187 discloses an antireflection film having a three-layer structure that is excellent in robustness to film thickness fluctuations. When the antireflection film having the above three-layer structure is installed on the surface of an image display device, the average value of surface reflectance can be reduced to 0.5% or less, reflection can be remarkably reduced, and stereoscopic effect can be reduced. Can be obtained. Further, each layer may be provided with other functions, for example, an antifouling low refractive index layer, an antistatic high refractive index layer, an antistatic hard coat layer, an antiglare hard coat layer, and the like. (For example, JP-A-10-206603, JP-A-2002-243906, JP-A-2007-264113, etc.) and the like.
The refractive index of the low refractive index layer is preferably 1.26 to 1.40, more preferably 1.28 to 1.38, and still more preferably 1.30 to 1.32. The thickness of the low refractive index layer is preferably 80 to 120 nm, more preferably 85 to 110 nm, and still more preferably 90 to 105 nm.
The refractive index of the high refractive index layer is preferably 1.55 to 1.85, more preferably 1.56 to 1.70. The thickness of the high refractive index layer is preferably 200 nm or less, and more preferably 50 to 180 nm.

<Adhesive layer>
The optical layered body of the present invention preferably further has an adhesive layer in addition to the above-described retardation plate, polarizer and protective layer. The pressure-sensitive adhesive layer may be provided on the surface of the retardation plate opposite to the surface on which the polarizer is provided, or may be provided between the retardation plate and the polarizer. It may be provided between the protective layers, and when it has a plurality of protective layers, it may be provided between the protective layers and is not particularly limited.
The pressure-sensitive adhesive layer may be appropriately selected from pressure-sensitive adhesives that can be applied to this type of optical laminate, and is formed of, for example, a PSA (Pressure Sensitive Adhesive) pressure-sensitive adhesive. More specifically, the layer formed with the acrylic adhesive is illustrated.

<Absorbing compound>
The optical layered body of the present invention contains a compound having absorption at 480 nm or less (also referred to as “absorbing compound” or “absorbing agent”).
Any layer of the optical laminate may contain the absorbing compound, but the above-mentioned adhesive layer or protective layer (including the hard coat layer) preferably contains the absorbing compound. Further, the retardation plate may contain the above-mentioned absorbing compound. For example, the retardation plate further includes a positive C plate having a positive C characteristic, and the positive C plate contains the absorbing compound. Is done. Furthermore, the semi-transmissive / semi-reflective film may contain an absorbing compound. Thus, when layers, such as an adhesion layer, a protective layer, a positive C plate, and a semi-transmissive semi-reflective film, contain an absorbing compound, it is preferable because the layer configuration is simplified. In addition, this invention is not limited to this, You may provide the layer containing an absorption compound separately. Moreover, it is preferable that the absorption compound is contained other than the outermost surface from a viewpoint of suppressing the color at the time of black display. The transflective film or the retardation layer may contain an absorbing compound, and the transferred alignment film layer may contain the absorbing compound. Moreover, an absorbing compound may be contained on the display element side of the transflective film, and is not particularly limited.
From the viewpoint of suppressing external light reflection, it is preferable that the absorbing compound is present in any layer on the translucent semi-reflective film or on the side opposite to the viewing side (the side where the display element is provided) of the transflective semi-reflective film. Further, from the viewpoint of improving luminance, it is preferable that an absorbing compound is present in any layer on the viewing side of the transflective film. In this case, it is preferable that the protective layer or the adhesive layer contains an absorbing compound.
The “compound having absorption at 480 nm or less” means a compound having a light transmittance of 10% or less by containing the compound at any wavelength of 480 nm or less.
The maximum absorption wavelength of the absorbing compound is preferably from 300 nm to 500 nm, more preferably from 350 nm to 450 nm, still more preferably from 370 nm to 440 nm, still more preferably from 380 nm to 430 nm. Even more preferably. Note that the maximum absorption wavelength means a wavelength at which the transmittance is most reduced or a wavelength at which the transmittance is 3% or less.

The absorbing compound is not particularly limited as long as it is a compound having absorption at a wavelength of 480 nm or less, but is preferably a compound having low absorption in a wavelength region of 500 nm to 780 nm. If the absorption in the wavelength region of 500 nm or more and 780 nm or less is large, the color may change when an image is displayed or a sufficient amount of light may not be obtained.
When the light transmittance in the region of 500 nm to 780 nm of the optical laminate not containing the absorbing compound is 100%, the light transmittance in the region of 500 nm to 780 nm of the optical laminate containing the absorbing compound is: Preferably it is 70% or more, More preferably, it is 80% or more, More preferably, it is 90% or more, More preferably, it is 95% or more.
That is, the absorbing compound is preferably a compound having absorption in a wavelength region of 480 nm or less and weak absorption of light in a wavelength region of 500 nm or more and 780 nm or less, or having no absorption in the wavelength region.

  The absorbing compound is not particularly limited as long as it has the above-mentioned characteristics. Specifically, the triazine ultraviolet absorber, the benzotriazole ultraviolet absorber, the benzophenone ultraviolet absorber, the oxybenzophenone ultraviolet absorber, A salicylic acid ester type ultraviolet absorber, a cyanoacrylate type ultraviolet absorber, etc. can be mentioned, These can be used individually by 1 type or in combination of 2 or more types.

Moreover, you may use the compound which the maximum absorption wavelength of an absorption spectrum exists in 300 nm or more and 480 nm or less instead of said ultraviolet absorber or in addition to said absorber. The maximum absorption wavelength of the compound is more preferably from 350 nm to 450 nm, and still more preferably from 380 nm to 430 nm.
The structure of the compound is not particularly limited. Examples of the dye compound include an organic dye compound and an inorganic dye compound. Among these, an organic dye is used from the viewpoint of maintaining dispersibility in a resin component such as a base polymer and transparency. Compounds are preferred.

Examples of the organic dye compound include azomethine compounds, indole compounds, cinnamic acid compounds, pyrimidine compounds, porphyrin compounds, and the like.
As the organic dye compound, a commercially available one can be suitably used. Specifically, as the indole compound, BONASORB UA3911 (trade name, absorption spectrum maximum absorption wavelength: 398 nm, Orient Chemical Industries, Ltd.) (Product name), BONASORB UA3912 (trade name, absorption spectrum maximum absorption wavelength: 386 nm, manufactured by Orient Chemical Industry Co., Ltd.), cinnamic acid-based compounds, SOM-5-0106 (trade name, absorption spectrum of Examples of the maximum absorption wavelength: 416 nm, manufactured by Orient Chemical Industry Co., Ltd., and pyrimidine compounds include FDB-009 (trade name, maximum absorption wavelength of absorption spectrum: 394 nm, manufactured by Yamada Chemical Industry Co., Ltd.) and the like. it can.

The content of the absorbing compound is not particularly limited and may be appropriately selected.
Moreover, an absorption compound may be used individually by 1 type, and may use 2 or more types together.

[Display panel and display device]
The display panel of the present invention is not particularly limited as long as the optical laminate of the present invention described above is provided with a display element. However, the display panel is particularly effective for a display panel having a high electrode reflectivity, and an organic electroluminescence display element (hereinafter referred to as an organic electroluminescence display element). , “Organic EL display element”) or a micro light-emitting diode display element (hereinafter “micro LED display element”) is preferable, and an organic electroluminescence display element is more preferable.
The display panel of the present invention preferably includes the optical laminate of the present invention on the light emitting surface of the display element. By providing the optical layered body of the present invention, it is possible to provide a display device capable of improving blue luminance and suppressing blue shift when observed from an oblique direction.

  In the present invention, the display element preferably has a microcavity structure. When the display element has a microcavity structure, the display device including the display element has a large viewing angle, that is, when viewed from an oblique direction, the resonance wavelength shifts to the short wavelength side, so the image is blue-shifted. The problem of doing is remarkable.

In the present invention, the difference between the blue emission peak wavelength of the display element and the reflection peak wavelength of the optical laminate is preferably 20 nm or less. In addition, the reflection peak wavelength of the optical laminate is a peak wavelength of a wavelength that exhibits a brightness enhancement effect by providing the optical laminate with respect to incident light from the display element side at 5 °. The difference between the blue emission peak wavelength of the display element and the reflection peak wavelength of the optical layered body is more preferably 15 nm or less, and further preferably 10 nm or less.
When the difference between the blue emission peak wavelength of the display element and the reflection peak wavelength of the optical layered body is 20 nm or less, there is little change in color in frontal observation, and a desired color is easily obtained. Further, it is preferable during oblique observation because blue shift is suppressed.

The display device of the present invention is not particularly limited as long as it includes the display panel of the present invention, but the display panel of the present invention, a drive control unit electrically connected to the display panel, and a housing for housing these. It is preferable to provide a body.
In the present invention, the display device is preferably an organic electroluminescence display device (hereinafter also referred to as “organic EL display device”). The display of this invention is not limited to this, A micro LED display apparatus may be sufficient. Since the organic EL display device and the micro LED display device have high electrode reflectivity, the problem of the present invention is particularly likely to occur, and the present invention is particularly suitable for these display devices. Among these, the display device is preferably an organic electroluminescence display device.
The organic EL display device is a display device in which a light emitting layer or a plurality of organic compound thin films including a light emitting layer are formed between a pair of electrodes of an anode and a cathode. The display panel of the present invention is provided on the viewing side of the organic EL display device. Have. In addition to the light emitting layer, the organic compound thin film may have a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, a protective layer, etc., and each of these layers has other functions. It may be. Each layer such as an electrode of an organic EL display device and an organic compound thin film can be formed by a known material / method.

Although it does not specifically limit as a display panel and a display apparatus of this invention, The display panel and display apparatus which are used in a state with a large viewing angle are suitable. Specifically, a portable information terminal, a large display device, a signage, and the like are exemplified.
Note that when used in a large display panel or display device, the viewing angle tends to be large, and the change in hue due to reflected light becomes more problematic. Therefore, a display device of 55 inches or more, or a display device of 55 inches or more. It is preferable that the display panel be used in the above. The size of the display device is more preferably 65 inches or more, and still more preferably 70 inches or more. The display panel is more preferably a display panel for a display device of 65 inches or more, and more preferably a display panel for a display device of 70 inches or more.
Although it does not specifically limit as a display panel and a display apparatus of this invention, The display panel and display apparatus which are used in a state with a large viewing angle are suitable. Specifically, a portable information terminal, a large display device, a signage, and the like are exemplified.

[Phase difference plate, polarizer, and transflective film]
The retardation plate, the polarizer, and the transflective film are the retardation plate, the polarizer, and the transflective film that are used in the display panel of the present invention.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail with reference to an Example and a comparative example, this invention is not limited to these Examples at all.

A sample having a layer structure shown in FIG. 3 was prepared. FIG. 3 is a cross-sectional view showing a sample manufactured for reflectance measurement.
The layers and compounds used in the examples are as follows.
・ Λ / 4 plate (reverse dispersion (Re450 / Re550 = 0.85), 142 nm)
A liquid crystal material of Re450 / Re550 = 0.85 diluted with a solvent (toluene / cyclopentanone = 7/3) to a solid content of 20% was coated on a PET substrate to prepare a retardation plate. The coating thickness was adjusted to achieve the above retardation value. Used by transferring from a PET substrate. The phase difference was measured by KOBRA-WR manufactured by Oji Scientific Co., Ltd.
TAC: FUJIFILM Corporation, TD60UL
Polarizer: iodine-doped stretched PVA
Hard coat layer: The following absorbent A is added as an absorbent compound to PET-30 manufactured by Nippon Kayaku Co., Ltd. so that the content in the hard coat layer is 5% by mass, and 3% of Irgacure 907 is added. The resultant was adjusted to have a thickness of 4 μm, cured with ultraviolet light, and used as a hard coat layer (refractive index = 1.53).
・ Adhesive layer: Lintec Co., Ltd. optical adhesive 10 μm thick product ・ Absorbing compound A: Orient Chemical Co., Ltd., BONASORB UA-3911
CLC layer: 93.25 parts by mass of polymerizable liquid crystalline monomer, 6.85 parts by mass of a chiral agent having acryloyl at both ends (Paliocolor (registered trademark) LC756, manufactured by BASF), a photopolymerization initiator (IRGACURE (registered trademark) 907; 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one) 4 parts by mass, acrylic leveling agent (BYK-361N, manufactured by Big Chemie Japan Co., Ltd.) 0.1 What diluted the mass part with cyclopentanone to 20% of solid content was coated on PET film, and the film provided with the liquid crystal layer (thickness 3.0 micrometers) which has a cholesteric structure was produced. The CLC layer was transferred from a PET substrate.

  In the experimental example and the comparative example, the angle formed by the absorption axis of the polarizer and the orientation axis of the inversely dispersive λ / 4 retardation plate was 45 °.

[Reflectance and transmittance measurement]
The optical laminated body shown in FIG. 3 was produced. The absorbing compound is contained in the hard coat layer located below the CLC layer.
FIG. 4 shows the transmittance measured with only the hard coat layer containing the absorbing compound (absorbent A in FIG. 4), the reflectance at an incident angle of 5 ° with the semi-transmissive semi-reflective film (CLC layer) alone (FIG. 4 and CLC), and the reflectance of the laminate shown in FIG. 3 at an incident angle of 5 ° with the CLC layer as the light incident surface (in FIG. 4, CLC + absorbent A).
In FIG. 4, the absorbent A is the transmittance of the hard coat layer containing the absorbing compound, and the wavelength at which the transmittance is 50% is 424 nm.
Further, in FIG. 4, CLC indicates the reflectance at an incident angle of 5 ° with the semi-transparent semi-reflective film alone, the peak wavelength of the reflectance is 431 nm, and the reflectance at the peak top is 35.3%. is there. Moreover, the half value width at this time was 73 nm.
Furthermore, in FIG. 4, CLC + absorbent A shows the reflectance at an incident angle of 5 ° of the laminate shown in FIG. 3, and the hard coat layer below the CLC layer contains the absorbent A as an absorbing compound. At this time, the peak wavelength of the reflectance was 444 nm, the reflectance at the peak top was 30.3%, and the half width at this time was 43 nm.

<Reflectance measurement>
The reflectance was measured by the following method.
The reflectance in the visible region (380 nm to 780 nm) was measured using a V-7100 (automatic absolute reflectance measuring unit: VAR-7010) manufactured by JASCO Corporation. The reflectance of light incident from the hard coat layer side of the sample shown in FIG. 3 was measured.

FIG. 5 shows the measurement results of the reflectance of the optical laminate shown in FIG. 3 with respect to incident light from 5 °, 25 °, and 45 °.
In FIG. 5, the average value (A) of the reflectance at 400 nm to 480 nm for 5 ° incident light is 18.4%, and the average reflectance from 400 nm to 480 nm for 45 ° reflected light. The value (B) was 9.8%, and B / A was 0.53.
The peak top at 5 ° is 30.3% (444 nm), the peak top at 25 ° is 26.7 (439 nm), and the peak top at 45 ° (peak top on the shortest wavelength side at 400 to 480 nm) is 14. .2 (433 nm).
The half width at 5 ° was 43 nm, and the half width at 25 ° was 32 nm.

In the optical layered body of the present invention, when any layer on the display element side of the transflective film or the transflective film contains an absorbing compound, the light incident from the display element side is the optical When the average value of the reflectance at a wavelength of 400 nm or more and 480 nm or less at an incident angle of 5 ° of the laminate is A and the average value of the reflectance at a wavelength of 400 nm or more and 480 nm or less at an incident angle of 45 ° is B, B / A is 0.00. It is preferable that it is 8 or less. When the B / A is 0.8 or less, the blue shift of the image is further suppressed when observed from an oblique direction, which is preferable.
The B / A is preferably 0.75 or less, more preferably 0.70 or less, still more preferably 0.60 or less, and still more preferably 0.50 or less.
The lower limit of B / A is not particularly limited, but the viewpoint of suppressing coloring of the optical laminate itself when there is no incident light, and the viewpoint of color reproducibility of display images of display panels and display devices including the optical laminate. Therefore, it is preferably 0.1 or more, more preferably 0.2 or more, and still more preferably 0.3 or more.

[Emission luminance evaluation with image display device (image evaluation)]
An organic EL display device is produced by using the produced optical laminate instead of the circularly polarizing plate of the organic EL display panel having a display element having a microcavity structure and each layer provided on the viewing side from the circularly polarizing plate. did.
Further, as a comparative example, an optical layered body that does not have a CLC layer and does not contain an absorbing compound was used.
Images of the obtained organic EL display device when displaying a white image were observed from angles of 0 ° (front), 20 °, and 40 °. In the comparative example, the maximum light emission luminance at 0 ° was set to 1.0, and the relative luminance was shown (see FIGS. 6 to 8). The light emission luminance was measured at a measurement angle of 2 ° and a measurement distance of 50 cm using a spectroradiometer SR-2 manufactured by TOPCON. Here, as a comparative example, in FIG. 3, the CLC layer and the hard coat layer were omitted, and an optical laminate was produced using a layer containing no absorbing compound as the hard coat layer.
As a result, in the comparative example, the ratio of the blue and red luminances at an angle (20 ° and 40 °) diagonally than the ratio of the blue and red luminances of the front [blue luminance of the front / red luminance of the front] [ Oblique blue luminance / oblique red luminance] was increased, and a white image was observed to be bluish when viewed obliquely as compared to the front view.
On the other hand, in the embodiment, the ratio of the front blue luminance and the red luminance [front blue luminance / front red luminance] and the diagonal (20 ° and 40 °) blue luminance and red luminance [oblique] [Brightness / oblique red luminance] is comparable, and the white image is bluish and difficult to be observed in oblique viewing as compared to front view. Furthermore, in the Example, the blue brightness | luminance improvement was seen by observation from the front. In addition, the brightness improvement of blue on the front side was not so extreme as to greatly affect the visibility.
Therefore, in the embodiment, it is considered that if the blue brightness of the front is suppressed by the panel design, the long life of the blue is achieved, and as a result, the long life of the organic EL display device is achieved. Note that the blue luminance can be adjusted by lowering the voltage. In addition, by adjusting the blue luminance in this way, the same color tone as that of a conventional display device can be achieved during frontal observation, and further, when observed from an oblique direction, the blue luminance is further reduced, and the blue color is further reduced. The shift is considered to be suppressed.

  According to the optical layered body of the present invention, it is possible to provide a display panel and a display device in which blue light emission luminance is improved during frontal observation and the blue shift of the image is suppressed even when observed from an oblique direction. It is.

10, 20 Optical layered body 12 CLC layer 14, 24 Retardation plate 16, 26 Polarizer 18 Circularly polarizing plate 22 DBEF layer

Claims (18)

An optical laminate having a transflective film, a retardation plate, and a polarizer,
The optical layered body contains a compound having absorption at 480 nm or less,
The optical laminated body, wherein the transflective film has a selective reflection wavelength of 380 nm or more and 480 nm.   The transflective film is a liquid crystal layer having a cholesteric structure, the retardation layer and the polarizer constitute a circularly polarizing plate, and the transflective film, the retardation film, and the polarizer are provided in this order. Item 2. The optical laminate according to Item 1.   For incident light from the liquid crystal layer side having a cholesteric structure, the liquid crystal layer having the cholesteric structure reflects right circularly polarized light and the circularly polarizing plate transmits left circularly polarized light, or the cholesteric structure is The optical laminate according to claim 2, wherein the liquid crystal layer has left circularly polarized light and the circularly polarizing plate transmits right circularly polarized light.   The optical laminate according to claim 2 or 3, wherein a reflection wavelength peak of the optical laminate is located on a long wavelength side with respect to a selective reflection center wavelength of the liquid crystal layer having the cholesteric structure.   The optical laminated body according to any one of claims 2 to 4, wherein a half-value width of a reflection peak of the optical laminated body is smaller than a half-value width of a reflection peak of the liquid crystal layer having the cholesteric structure alone.   Furthermore, the optical laminated body in any one of Claims 1-5 which has a protective layer.   Furthermore, the optical laminated body in any one of Claims 1-6 which has an adhesion layer.   The optical laminated body according to any one of claims 1 to 7, wherein the retardation plate is a quarter-wave retardation plate.   The optical laminate according to any one of claims 1 to 7, wherein the retardation plate is a laminate of a quarter-wave retardation plate and a half-wave retardation plate.   The optical laminated body according to claim 8 or 9, wherein the retardation plate further comprises a positive C plate.   A display panel provided with the optical laminated body in any one of Claims 1-10 on the light-projection surface of a display element.   The display panel according to claim 11, wherein the display element has a microcavity structure.   The display panel according to claim 11 or 12, wherein a difference between a blue light emission peak wavelength of the display element and a reflection peak wavelength of the optical laminate is 20 nm or less.   A display apparatus provided with the display panel in any one of Claims 11-13.   The display device according to claim 14, wherein the display device is an organic electroluminescence display device.   The phase difference plate used for the display panel in any one of Claims 11-13.   The polarizer used for the display panel in any one of Claims 11-13.   A transflective film used for the display panel according to claim 11.