WO2021131413A1 - Image display device - Google Patents

Abstract

[Problem] To provide an image display device that can display an image in a desired color state while ensuring the product life of the image display device. [Solution] The image display device according to one embodiment comprises: an image display unit that includes a light source and displays an image on an image display screen; a λ/4 phase difference layer provided on the image display screen; and a linear polarizing layer provided on the λ/4 phase difference layer. Light emitted from the light source has a spectral region that includes a light emission peak and has a full width at half maximum of 60 nm or smaller; and the λ/4 phase difference layer is configured such that, in an interference spectrum based on both surfaces of the λ/4 phase difference layer in the thickness direction, the number of local maxima is one and the number of local minima is two or fewer within the wavelength range defining the full width at half maximum. FIG. 1:

Description

Image display device

The present invention relates to an image display device.

As an image display device, a device including an image display unit including a light emitting unit, a λ / 4 retardation layer, and a linearly polarized light layer in this order from the back side to the front side is known (see, for example, Patent Document 1). .. An example of the image display unit is a flat panel display device (for example, a thin liquid crystal display device, a thin organic electroluminescence image display device, or the like).

JP-A-2019-79053

When the image display device displays, for example, a color image, a light emitting unit that outputs three primary color lights (red, blue, green) is used. Due to the influence of the material for outputting each color, for example, even if the light emitting part (or light emitting element) that outputs red, blue, and green is driven under the same conditions, the intensity of light of a specific color becomes weak and is displayed. It may be difficult to display the original color that should be displayed. If a light emitting unit (light emitting element) that outputs the above specific color is used with high brightness in order to eliminate such a problem, the life of the light emitting unit is shortened, and as a result, the product life of the image display device is shortened. It gets shorter.

Therefore, an object of the present invention is to provide an image display device capable of displaying an image in a desired color state while ensuring the product life of the image display device.

The image display device according to the present invention includes an image display unit that includes a light emitting unit and displays an image on the image display surface, a λ / 4 phase difference layer provided on the image display surface, and the λ / 4 phase difference. A linearly polarized light layer provided on the layer is provided, and the light from the light emitting portion has a mountain-shaped region including a light emitting peak and a half-value total width of 60 nm or less, and the λ / 4 retardation layer is a condition 1. It is configured to meet the requirements.
Condition 1: In the interference spectrum based on both sides in the thickness direction of the λ / 4 retardation layer, the number of maximum values within the wavelength range defining the full width at half maximum is one and the number of minimum values is two or less. is there.

In the above configuration, even if the intensity of light that is output from the light emitting unit and has an emission spectrum including the mountain-shaped region is weak, the mountain-shaped region is formed based on the interference of both sides of the λ / 4 retardation layer. The corresponding color can be enhanced. Therefore, for example, even if the intensity of one of the three primary colors is weak, that color can be enhanced by the interference effect of the λ / 4 retardation layer, so that the image can be displayed in a desired color state. Further, since the color is enhanced by the interference effect of the λ / 4 retardation layer, deterioration of the light emitting portion can be suppressed. As a result, the product life of the image display device can be ensured.

The λ / 4 retardation layer may be configured so as to further satisfy the condition 2.
Condition 2: The difference between the peak wavelength corresponding to the emission peak and the wavelength corresponding to the maximum value in the interference spectrum is 1/5 or less of the full width at half maximum.

The full width at half maximum is 20 nm, and the peak wavelength corresponding to the emission peak may be 458 ± 2 nm.

The full width at half maximum is 40 nm, and the peak wavelength corresponding to the emission peak may be 523 ± 2 nm.

The full width at half maximum is 40 nm, and the peak wavelength corresponding to the emission peak may be 530 ± 2 nm.

The full width at half maximum is 50 nm, and the peak wavelength corresponding to the emission peak may be 626 ± 2 nm.

The λ / 4 phase difference layer may be a phase difference expression layer that gives λ / 4 phase difference to light.

The λ / 4 retardation layer may include a retardation expression layer that imparts a λ / 4 phase difference to light and a non-oriented layer. In this case, the thickness of the λ / 4 retardation layer can be adjusted by the non-oriented layer.

The retardation layer and the non-oriented layer are laminated in close contact with each other, and the difference in refractive index between the retardation layer and the non-oriented layer may be zero. In this case, substantially no reflection occurs at the interface between the retardation expression layer and the non-oriented layer.

The λ / 4 retardation layer has a first surface in the thickness direction and a second surface opposite to the first surface, and includes the first surface and the second surface from the light emitting unit. Of the refractive index differences at each of the plurality of interfaces through which the output light passes, the refractive index difference when the first surface and the second surface are interfaces may be larger than the other refractive index differences.

In this case, in the spectrum of the light output from the image display device, the interference based on the reflection on the first surface and the second surface becomes dominant, and the color corresponding to the mountain-shaped region is λ / 4 phase difference. Easy to augment with layer interference.

According to the present invention, it is possible to provide an image display device in which a change in hue of external light reflected light is suppressed when viewed from an oblique direction.

FIG. 1 is a schematic diagram showing a schematic configuration of an image display device according to an embodiment. FIG. 2 is a conceptual diagram of a mountain-shaped region included in the emission spectrum of the light output from the light emitting unit. FIG. 3 is a schematic diagram showing a schematic configuration of the simulation. FIG. 4 is a schematic diagram illustrating an emission spectrum used in the simulation. FIG. 5 is a chart showing the parameters used in the simulation. FIG. 6 is a chart showing the parameters used in the simulation. FIG. 7 is a chart showing the parameters used in the simulation. FIG. 8 is a chart showing the results of the simulation. FIG. 9 is a chart showing the results of the simulation. FIG. 10 is a chart showing the results of the simulation.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same elements are designated by the same reference numerals, and duplicate description will be omitted. The dimensional ratios in the drawings do not always match those described.

FIG. 1 is a schematic diagram showing a schematic configuration of an image display device 1 according to an embodiment. The image display device 1 has an image display unit 10 and an optical laminate 20. The optical laminate 20 is laminated on the image display unit 10. Since the image can be seen from the optical laminate 20 side, in the image display device 1, the optical laminate 20 side may be referred to as the front side and the image display unit 10 side may be referred to as the back side.

[Image display]
The image display unit 10 is a device that outputs an image. The image display unit 10 has an image display surface 10a for displaying (or outputting) an image. An example of the image display unit 10 is a flat panel display device. The display device exemplified as the image display unit 10 is a device in a state in which a member for optical compensation is not included on the image display surface 10a.

As shown in FIG. 1, the image display unit 10 according to the embodiment includes a light source unit 11 and an image display layer 12. An example of an image display unit 10 having a light source unit 11 and an image display layer 12 separate from the light source unit 11 is a liquid crystal display device. Examples of the liquid crystal display device include any of a transmissive liquid crystal display device, a semi-transmissive liquid crystal display device, and the like.

[Light source]
The light source unit 11 supplies illumination light (tatab backlight) to the image display layer 12. The light source unit 11 has a light emitting unit 111. As shown in FIG. 2, the light emitting unit 111 outputs light having a mountain-shaped region M including a light emitting peak and having a full width at half maximum of 60 nm or less. FIG. 2 is a conceptual diagram of a mountain-shaped region M included in the emission spectrum of the light output from the light emitting unit 111.

Hereinafter, for convenience of explanation, the wavelength corresponding to the emission peak of the mountain-shaped region M is referred _{to as a peak wavelength λ 0.} The lower limit wavelength (the wavelength on the short wavelength side of the above wavelength range) in the wavelength range that defines the half-value full width of the mountain-shaped region M _{is referred to as wavelength λ 1,} and the upper limit wavelength (the wavelength on the long wavelength side of the above wavelength range) is referred to as wavelength λ 1. It is called wavelength λ _2.

An example of the light emitting unit 111 is an LED. When the light emitting unit 111 is a point light source such as an LED, the light source unit 11 has a plurality of light emitting units 111 as schematically shown in FIG. The light emitting unit 111 may output light including, for example, the three primary colors (red, green, and blue). An example of such a light emitting unit 111 is, for example, a white LED. When the light emitting unit 111 outputs light containing the three primary colors, the emission spectrum of the light output from the light emitting unit 111 has a mountain-shaped region for each of the colors corresponding to the three primary colors. In this case, at least one of the red, green and blue mountain-shaped regions satisfies the condition of the mountain-shaped region M. Alternatively, the light source unit 11 may include a light emitting unit 111 that outputs blue, a light emitting unit 111 that outputs green, and a light emitting unit 111 that outputs red. In this case, the emission spectrum of the light output from at least one of the blue, green, and red light emitting units 111 has the mountain-shaped region M.

As an example of the mountain-shaped region M, the first to fourth mountain-shaped regions shown in Table 1 may be used by combining _{the peak wavelength λ 0 and the full width at half maximum.} Table 1 also shows the colors corresponding to the first to fourth chevron regions.





[Table 1]

[Image display layer]
The image display layer 12 is a layer that has a plurality of pixels and forms an image by controlling the transmission state of the illumination light from the light source unit 11. The image display layer 12 is, for example, a liquid crystal layer.
In the form shown in FIG. 1, the surface of the image display layer 12 opposite to the light source unit 11 is the image display surface 10a.

The image display unit 10 according to the embodiment may have a self-luminous image display layer 12 in which the pixels themselves of the image display layer 12 function as the light emitting unit 111. In this case, as shown in FIG. 1, the light source unit 11 separated from the image display layer 12 is unnecessary. An example of the self-luminous image display layer 12 is an organic electroluminescence (organic EL) image display element. Even if the image display layer 12 is a self-luminous layer, an example of a mountain-shaped region M having an emission spectrum of light output by a pixel (light emitting unit 111) includes a light source unit 11 and an image as shown in FIG. This is the same as when the display layer 12 is separated.

[Optical laminate]
The optical laminate 20 has a λ / 4 retardation layer 21 and a linearly polarized light layer 22. The optical laminate 20 is a member that optically compensates the image displayed on the image display surface 10a. The optical laminate 20 functions as, for example, a circular polarizing plate or an elliptical polarizing plate.

[Λ / 4 phase difference layer]
The λ / 4 retardation layer 21 is an optical functional layer that imparts a phase difference of λ / 4 (1/4 wavelength) to light passing through (or transmitting) through the λ / 4 retardation layer 21. An example of the thickness of the λ / 4 retardation layer 21 is 0.5 μm to 5.0 μm. An example of the refractive index of the λ / 4 retardation layer 21 is 1.50 to 1.70. The λ / 4 retardation layer 21 is bonded to the image display unit 10 via the pressure-sensitive adhesive layer 2a.

The pressure-sensitive adhesive layer 2a can be composed of a pressure-sensitive adhesive composition containing a resin as a main component, such as (meth) acrylic type, rubber type, urethane type, ester type, silicone type, and polyvinyl ether type. Among them, a pressure-sensitive adhesive composition using a (meth) acrylic resin having excellent transparency, weather resistance, heat resistance and the like as a base polymer is preferable. The pressure-sensitive adhesive composition may be an active energy ray-curable type or a thermosetting type. The thickness of the pressure-sensitive adhesive layer 2a is usually 3 μm to 30 μm, preferably 3 μm to 25 μm. An example of the refractive index of the pressure-sensitive adhesive layer 2a is 1.40 to 1.55.

[Straightly polarized layer]
The linearly polarized light layer 22 is an optical functional layer having linearly polarized light characteristics. The linearly polarizing layer 22 is, for example, a linear polarizing plate. The linearly polarizing layer 22 has a polarizing film (polarizer layer) having linearly polarizing characteristics and a protective film that protects the polarizing film. An example of the thickness of the linearly polarizing layer 22 is 12 μm to 140 μm.

An example of a polarizing film is a film in which a dichroic dye is adsorbed and oriented on a uniaxially stretched resin film. The polarizing film is not particularly limited as long as it is a resin film having linear polarization characteristics, and may be, for example, one used for a known linear polarizing plate.

Examples of the resin film as the polarizing film include a polyvinyl alcohol (hereinafter sometimes referred to as “PVA”) resin film, a polyvinyl acetate resin film, an ethylene / vinyl acetate resin film, a polyamide resin film, and a polyester resin film. .. Usually, a PVA-based resin film, particularly a PVA film, is used from the viewpoint of the adsorptivity and orientation of the dichroic dye.

An example of the thickness of the polarizing film is 2.0 μm to 40 μm. An example of the refractive index of a polarizing film is 1.50 to 1.60.

The protective film is laminated on the polarizing film. The protective film is, for example, a resin film (for example, a triacetyl cellulose (hereinafter, also referred to as “TAC”) -based film), a glass cover, or a glass film. An example of the thickness of the protective film is 10 μm to 100 μm. An example of the refractive index of the protective film is 1.40 to 1.70.

The linearly polarizing layer 22 may have two protective films against, for example, a polarizing film. In this case, protective films are laminated on both sides of the polarizing film. Examples of the material, thickness and refractive index of each of the two protective films are as described above. The materials, thickness and refractive index of the two protective films may be the same or different.

The linearly polarizing layer 22 may be manufactured by preparing long members, laminating the respective members by roll-to-roll, and then cutting the members into a predetermined shape, or forming each member into a predetermined shape. It may be manufactured by cutting and then laminating.

The linearly polarized light layer 22 is bonded to the λ / 4 retardation layer 21 via the pressure-sensitive adhesive layer 2b. The example of the pressure-sensitive adhesive layer 2b is the same as that of the pressure-sensitive adhesive layer 2a.

In the form in which the linearly polarizing layer 22 has one protective film against the polarizing film, the linearly polarizing layer 22 is usually arranged closer to the λ / 4 retardation layer 21 so that the linearly polarizing layer 22 is λ / 4. It is bonded to the retardation layer 21.

The image display device 1 is manufactured as follows, for example.

The λ / 4 retardation layer 21 and the linearly polarized light layer 22 are manufactured, respectively. After that, the optical laminate 20 is formed by laminating them. Next, the image display device 1 is manufactured by bonding the optical laminate 20 to the image display unit 10 via the pressure-sensitive adhesive layer 2a. When the optical laminate 20 is attached to the image display unit 10, the λ / 4 retardation layer 21 is arranged closer to the image display unit 10.

In the image display device 1 according to the embodiment, for example, among the refractive index differences at each of a plurality of interfaces including the first surface 21a and the second surface 21b and through which the light output from the light emitting unit 111 passes, the first surface 21a The difference in refractive index when each of the second surface 21b is an interface is larger than the difference in refractive index of the other. The difference in refractive index at the interface means the difference in refractive index on both sides of the interface. Such a difference in refractive index can be realized, for example, by adjusting the materials constituting each layer.

Next, the λ / 4 retardation layer 21 will be further described. As shown in FIG. 1, the λ / 4 retardation layer 21 has a retardation expression layer 211 and an unoriented layer 212.

The phase difference expression layer 211 is a layer that functions as a λ / 4 retardation layer 21 only with the phase difference expression layer 211. The retardation layer 211 can be formed, for example, by a known material and forming method used for a quarter wave plate.

The retardation expression layer 211 may be a stretched resin film obtained by stretching a resin film. The retardation expression layer 211 may be, for example, a layer formed by a cured product obtained by curing the polymerizable liquid crystal compound in a unidirectional orientation. As the polymerizable compound, for example, a compound exhibiting reverse dispersibility is preferably used.

The type of the above-mentioned polymerizable liquid crystal compound is not particularly limited, but can be classified into a rod-shaped type (rod-shaped liquid crystal compound) and a disk-shaped type (disk-shaped liquid crystal compound, discotic liquid crystal compound) according to its shape. Further, there are a low molecular weight type and a high molecular weight type, respectively. The polymer generally refers to a polymer having a degree of polymerization of 100 or more (see "Polymer Physics / Phase Transition Dynamics, Masao Doi, p. 2, Iwanami Shoten, 1992").

Any polymerizable liquid crystal compound can be used for the retardation expression layer 211. Further, two or more kinds of rod-shaped liquid crystal compounds, two or more kinds of disc-shaped liquid crystal compounds, or a mixture of rod-shaped liquid crystal compounds and disc-shaped liquid crystal compounds may be used.

As the rod-shaped liquid crystal compound, for example, those described in claim 1 of JP-A-11-513019 or paragraphs [0026] to [0998] of JP-A-2005-289980 can be preferably used. .. As the disk-shaped liquid crystal compound, for example, those described in paragraphs [0020] to [0067] of JP-A-2007-108732 or paragraphs [0013] to [0108] of JP-A-2010-244038 are preferable. Can be used for.

Two or more types of polymerizable liquid crystal compounds may be used in combination. In that case, at least one type has two or more polymerizable groups in the molecule. That is, the cured layer of the polymerizable liquid crystal compound is preferably a layer formed by fixing a liquid crystal compound having a polymerizable group by polymerization. In this case, it is no longer necessary to exhibit liquid crystallinity after forming a layer.

The polymerizable liquid crystal compound has a polymerizable group capable of carrying out a polymerization reaction. As the polymerizable group, for example, a functional group capable of an addition polymerization reaction such as a polymerizable ethylenically unsaturated group or a ring-polymerizable group is preferable.
More specifically, examples of the polymerizable group include a (meth) acryloyl group, a vinyl group, a styryl group, an allyl group and the like. Among them, the (meth) acryloyl group is preferable. The (meth) acryloyl group is a concept that includes both a meta-acryloyl group and an acryloyl group.

The phase difference expression layer 211 has, for example, an A plate. The A plate can be formed, for example, by the above-mentioned polymerizable liquid crystal compound. In this case, the A plate is a horizontally oriented liquid crystal cured film. The retardation expression layer 211 may further have a horizontal alignment film for the A plate. The retardation expression layer 211 as a laminate of the horizontal alignment film and the A plate is formed by forming the horizontal alignment film and the A plate in this order on a support base material such as a resin film, and then peeling off the support base material. Can be manufactured.

When the retardation expression layer 211 is a laminated body, each layer constituting the retardation expression layer 211 is formed so as to have substantially the same refractive index so that reflection does not occur at the interface between the layers. This may be achieved, for example, by selecting the material of each layer so that each layer has the same refractive index, or by adjusting the refractive index by appropriately adding an additive to the material of each layer.

The non-oriented layer 212 is laminated in close contact with the retardation expression layer 211. The non-oriented layer 212 is arranged closer to the image display unit 10 in the λ / 4 retardation layer 21. The non-oriented layer 212 is a layer for adjusting the thickness of the λ / 4 retardation layer 21. The in-plane retardation of the non-oriented layer 212 is less than 0.1 nm (that is, substantially 0), and is a layer that does not contribute to imparting a retardation to light. The non-aligned layer 212 has substantially the same refractive index as the refractive index of the retardation developing layer 211 so that reflection does not occur at the interface between the non-oriented layer 212 and the retardation expressing layer 211. For example, the difference in refractive index on both sides of the interface between the non-oriented layer 212 and the phase difference expressing layer 211 is less than 0.02 (substantially zero). The non-oriented layer 212 is, for example, a layer formed by a cured product obtained by curing an ultraviolet (UV) adhesive. The UV adhesive may contain thiophene, thiourethane, carbazole, fluorene and the like as additives. Such additives can be used to adjust the refractive index.

The λ / 4 retardation layer 21 may be a layer formed only of the retardation expression layer 211 (that is, a configuration having no unoriented layer 212).

The λ / 4 retardation layer 21 is configured to satisfy the following condition 1.
[Condition 1]
In the interference spectrum based on both sides (first surface 21a and second surface 21b) in the thickness direction of the λ / 4 retardation layer 21, the wavelength range (λ ₁ or more and λ ₂ or less) that defines the full width at half maximum of the mountain-shaped region M. The number of maximum values in the range) is one, and the number of minimum values is two or less.

The interference spectrum is the light including the wavelength range defining the half-value full width of the mountain-shaped region M in the configuration of the image display device 1 including the λ / 4 retardation layer 21 (for example, when the mountain-shaped region M corresponds to blue). When light with a wavelength of 400 nm to 500 nm is incident on the λ / 4 retardation layer 21, the reflection of the first surface 21a (back surface side interface) and the second surface 21b (front surface side interface) of the λ / 4 retardation layer 21 It is an interference spectrum generated by.

When the image display unit 10 has a light emitting unit 111 that outputs the three primary colors (red, green, blue), or has a light emitting unit 111 corresponding to each of the three primary colors, the mountain-shaped region M for each color (red, green, blue) Is assumed. In this case, the mountain-shaped region M of condition 1 is a mountain-shaped region M corresponding to any of red, green, and blue. For example, it is a mountain-shaped region corresponding to blue, and in this case, the mountain-shaped region M may be the first mountain-shaped region shown in Table 1.

When the λ / 4 retardation layer 21 has the non-oriented layer 212, the first surface 21a is the surface of the non-oriented layer 212 opposite to the phase difference expressing layer 211 (in other words, the surface on the image display unit 10 side). The second surface 21b is a surface of the phase difference expression layer 211 opposite to the non-oriented layer 212 (in other words, a surface on the linearly polarized light layer 22 side). When the λ / 4 retardation layer 21 does not have the non-oriented layer 212, the first surface 21a is the surface on the image display portion 10 side of the retardation expression layer 211, and the second surface 21b is the retardation expression layer 211. It is a surface on the linearly polarized light layer 22 side in the above.

The λ / 4 retardation layer 21 may be configured to further satisfy the following condition 2.
[Condition 2]
The difference between the wavelength corresponding to the maximum value in the interference spectrum and the peak wavelength λ ₀ is 1/5 or less of the full width at half maximum of the mountain-shaped region M.

Condition 1 can be realized by adjusting the thickness and refractive index of the λ / 4 retardation layer 21. For example, by increasing the refractive index of the λ / 4 retardation layer 21, the thickness of the λ / 4 retardation layer 21 can be reduced, so that the above condition 1 can be easily satisfied. The same applies to condition 2.

The maximum value in the interference spectrum described in Condition 1 is caused by the interference between the interfaces of the λ / 4 retardation layer 21 (between the first surface 21a and the second surface 21b). When the distance between the interfaces (thickness of the λ / 4 retardation layer 21) changes slightly, the wavelength of the maximum value changes significantly. For example, even if the thickness is 1.890 μm and has a maximum value of 455 nm, if the thickness changes slightly (± 0.050 μm) to 1.940 μm or 1.890 μm, the peak value of the maximum value in the interference spectrum is reached. The wavelength deviates from the vicinity of 455 nm and becomes 442 nm or 468 nm, and 455 nm conversely becomes a minimum peak.

Therefore, for example, the λ / 4 retardation layer 21 is preferably manufactured by precision coating (for example, a coating method with a wet film thickness accuracy of several tens of nm). An example of the precision coating method will be described.

(Precision coating method)
Precision coating with a wet film thickness accuracy of several tens of nanometers can be realized by, for example, a slot die coating method, a spin coating method, a gravure coating method, or the like. In any of the methods, a coating liquid having a low solid content concentration and a low viscosity was used, the temperature and concentration of the coating liquid were stabilized, the time from the coating liquid application process to the drying process was shortened as much as possible, and it was stable. A drying step in an air stream, an active energy ray irradiation step at an optimum irradiation amount, and the like are preferable.

Further, by precisely feeding back the control items in each coating method to the measurement results of the film thickness and the phase difference value of the obtained dried coating material, precision coating can be realized more reliably.
In the slot die coating method, the discharge amount from the die lip, the lip shape, and the distance between the die lip and the base material to be coated are important control items. In the spin coating method, airflow stabilization in the coating environment, spinner rotation speed and dripping amount are important control items.

In the gravure coat method, the speed of the gravure roll and the speed ratio of the gravure roll and the backup roll are important control items.

When the λ / 4 retardation layer 21 is the retardation expression layer 211 (that is, when the non-alignment layer 212 is not provided), the retardation expression layer 211 may be manufactured by using the precision coating.

When the λ / 4 retardation layer 21 has the non-oriented layer 212, the thickness can be adjusted by the non-oriented layer 212. In this case, the retardation expression layer 211 may be formed by the same method as, for example, a known method for forming a 1/4 wave plate, while the non-oriented layer 212 may be formed by the above precision coating.

For example, an example in which an unoriented layer 212 having a refractive index of about 1.61 is formed so as to precisely control the thickness will be described. In this case, a bisphenol fluorene-based acrylate monomer (OGSOLEA-0200 manufactured by Osaka Gas Chemical Co., Ltd.) and a photoradical polymerization initiator (Irgacure 907 manufactured by BASF) are dissolved in a toluene solution at a mass ratio of 97: 3 to prepare a solution having a solid content concentration of 5%. Then, a coating solution is obtained, the coating solution is applied onto the retardation-developing layer 211 with a spin coater, dried, and UV-irradiated to obtain a non-oriented layer 212 whose thickness is precisely controlled. ..

As described above, the wavelength of the maximum value of the interference spectrum under condition 1 depends on the distance between the interfaces. Therefore, the thickness of the λ / 4 retardation layer 21 can be adjusted, and the non-oriented layer 212 functions as an interference control layer.

In the image display device 1, the λ / 4 retardation layer 21 satisfies the above-mentioned condition 1. As a result, in the light output from the light emitting unit 111 included in the image display unit 10, the light corresponding to the mountain-shaped region M is strongly colored by the image display device 1.

As a result, for example, even when the intensity of any of the three primary colors is lower than that of the other color, the intensity of the reduced state of that color with respect to the other color is affected by the interference action on both sides of the λ / 4 retardation layer 21. Can be compensated by. As a result, nature can achieve color development (desired color state). Further, in order to eliminate the intensity decrease state, for example, it is not necessary to improve the brightness of the light emitting unit 111 that outputs the color in which the intensity is decreased, so that the deterioration of the light emitting unit 111 can be suppressed. As a result, both the image display device 1 and the product life can be ensured.

For example, a blue light emitting material has a problem in the stability of a compound, and it is known that the life of a light emitting element (light emitting part) is impaired when used at high brightness. This is particularly noticeable in the case of organic light emitting devices, and is often applied to compounds containing a styrylamino group, which are often used as blue light emitting compounds.

Even in such a case, by setting the mountain-shaped region M under the condition 1 satisfied by the λ / 4 retardation layer 21 as the region corresponding to the blue color, the blue color becomes the interference action in the λ / 4 retardation layer 21. Can develop colors stronger than, for example, green and red. As a result, it is possible to maintain natural color development while weakening the emission intensity of blue light and extending the life of the light emitting unit 111.

When the λ / 4 retardation layer 21 further satisfies the condition 2, weakening due to interference can be reduced, so that a desired color state can be more easily realized. In order to reduce weakening due to interference, it is more preferable that the wavelength corresponding to the maximum value in the interference spectrum and the peak wavelength λ _{0 match.}

In one embodiment, among the refractive index differences at each of the plurality of interfaces through which the light output from the light emitting unit 111 passes, the refractive index difference when the first surface 21a and the second surface 21b are interfaces is the other. Greater than the difference in refractive index. In this case, the interference component contained in the spectrum of the light output from the linearly polarized light layer 22 is greatly affected by the interference based on both surfaces (back surface side interface and front side interface) of the λ / 4 retardation layer 21. Therefore, the effect of enhancing the light by the interference action based on the λ / 4 retardation layer 21 is more effective.

Next, it was verified by simulation that the color corresponding to the mountain-shaped region M could be strengthened by satisfying condition 1. The verification simulation will be described.

In the simulation, the image display device 30 shown in FIG. 3 was used as a simulation model. The image display device 30 includes an image display unit 31, an adhesive layer 32a, a λ / 4 retardation layer 33, an adhesive layer 32b, and a linearly polarizing layer 34. The pressure-sensitive adhesive layer 32a, the λ / 4 retardation layer 33, the pressure-sensitive adhesive layer 32b, and the linearly polarized light layer 34 are laminated on the image display unit 31 in this order. The λ / 4 retardation layer 33 has an unaligned layer 331 on the pressure-sensitive adhesive layer 32a side and a retardation expression layer 332 on the non-oriented layer 331. It is assumed that the image display device 30 is arranged in the air.

The image display unit 31, the pressure-sensitive adhesive layer 32a, the λ / 4 retardation layer 33, the pressure-sensitive adhesive layer 32b, the linearly polarized light layer 34, the non-aligned layer 331, and the retardation-developing layer 332 are the image display unit 10, the pressure-sensitive adhesive layer 2a, respectively. , Λ / 4 retardation layer 21, pressure-sensitive adhesive layer 2b, linearly polarizing layer 22, non-oriented layer 212, and retardation expression layer 211.

In the description of the simulation, the refractive indexes of the image display unit 31, the non-oriented layer 212, the retardation expression layer 211, and the linearly polarized light layer 34 are referred _{to as n G} , n _R , n _R , and n _{P, respectively. The refractive index n G} of the image display unit 31 is the refractive index of the portion adjacent to the pressure-sensitive adhesive layer 32a (that is, the portion in contact with the image display unit 31 side at the interface between the image display unit 31 and the pressure-sensitive adhesive layer 32a). .. It was assumed that the non-oriented layer 212 and the retardation layer 211 had the same refractive index. Therefore, the refractive index of the λ / 4 retardation layer 33 was _{also n R.} Refractive index of the adhesive layer 32a and the adhesive layer 32b is also the same, referred to the refractive index of the adhesive layer 32a and the adhesive layer 32b and the _{n PSA.}

In the simulation performed, the values in Table 2 were used for _{n G} , n _PSA , n _R , and n _P.
The refractive index shown in Table 2 is the refractive index with respect to a wavelength of 550 nm. The numerical value of each refractive index shown in Table 2 is the refractive index corresponding to the material expected to be used in each layer of the image display device 1.
_{The refractive index n G} of the image display unit 31 was defined as the refractive index of glass. This is because the portion of the image display portion 31 in contact with the pressure-sensitive adhesive layer 32a is often made of glass as a sealing material (or protective member), for example. Table 2 also shows the refractive index of the air outside the linearly polarized light layer 34.
[Table 2]

In the simulation, it is assumed that the light is output from the image display unit 31 in the above-mentioned mountain-shaped region M output from the light emitting unit 111. The conditions and theory of computation used in the simulation will be described below.

<Full width at half maximum of emission spectrum>
As shown in FIG. 4, the emission spectrum of the light output from the image display unit 31 is a monomodal continuous function f (λ) having a wavelength λ, and a spectrum having _{one maximum value f (λ 0).} The two wavelengths λ satisfying f (λ _{0 ) / 2 were set to wavelength λ 1} and wavelength λ ₂ (where λ ₂ > λ ₁ ), respectively, as in the case of FIG. In this case, the full width at half maximum of the mountain-shaped region M represented by the monomodal continuous function f (λ) is calculated by _{λ 2-} λ _1.

<Extreme value of interference spectrum>
The interference spectrum is a continuous trigonometric function in which the extreme values obtained by interference are taken in the order of maximum value, minimum value and maximum value, or in the order of maximum value, maximum value and minimum value from short wavelength to long wavelength. ..

As shown in FIG. 3, the optical path A is an optical path that reflects and travels in this order between the front interface (corresponding to the second surface 21b) and the back interface (corresponding to the first surface 21a) of the λ / 4 retardation layer 33. An optical path that is not reflected at any interface but is transmitted and travels is referred to as an optical path B. In the interference caused by the difference between the optical path A and the optical path B, the strengthening condition and the weakening condition are expressed as follows.
Strengthening conditions:

Weakness condition:

In the above-mentioned strengthening condition and weakening condition, ΔL is the optical path difference between the optical path A and the optical path B, and is represented by the following equation.

Here, d _R is the thickness of the λ / 4 retardation layer 33, and is the sum of the thicknesses of the non-oriented layer 212 and the retardation expression layer 211.

From the above strengthening condition and weakening condition, the wavelength λ _{in corresponding to the maximum value and the wavelength λ out} corresponding to the minimum value are expressed by the following equations.

In this simulation, the wavelength dispersion is not considered in the λ / 4 retardation layer 33. However, for example, when there is wavelength dispersion, the wavelength λ _k having a maximum value and a minimum value is calculated using the refractive index n _R (λ _{k) corresponding to each wavelength.}

<Intensity of interference spectrum>
Reflectivity r _{1 ~} r ₄ of each layer interface shown in FIG. 3 is expressed as follows by using the refractive index of each layer. The reflectance r1 is the reflectance at the interface between the image display unit 31 and the pressure-sensitive adhesive layer 32a. Reflectivity r ₂ is the reflectivity of the interface between the lambda / 4 of the phase difference layer 33 adhesive layer 32a interfaces and lambda / 4 retardation layer 33 the adhesive layer 32b. Reflectance r ₃ is the reflectivity of the interface between the adhesive layer 32b and the linear polarization layer 34. Reflectance r ₄ is the reflectivity of the interface between the linear polarization layer 34 and air.

When the intensity of the optical field of the output light from the inside of the image display unit 10 and E _0, the energy E _A of the optical field of the optical path A and the optical path B shown in FIG. _3, E _B is expressed by the following equation.

The intensities of the photoelectric field strength E _in under the strengthening condition and the photoelectric field strength E _out under the weakening condition are expressed by the following equations.

Optical field intensity E _n in interference-free conditions can be expressed by the following equation.

<Evaluation method>
The brightness of blue, green, and red emitted from the image display device 30 is proportional to the integrated value of these emission spectra S (λ). Multiply the emission spectrum S (λ) by the intensity amplitude spectrum (corresponding to the interference spectrum) E (λ) due to the interference of both sides (back surface side interface and front side interface) of the λ / 4 retardation layer 33, and the emission interference spectrum E ( λ) × S (λ) is obtained. The brightness of light emission under the strengthening interference condition and the weakening interference condition was evaluated using the integrated value P of the light emission interference spectrum.

The range of wavelength λ to be integrated was set to _{two wavelengths λ satisfying f (λ 0} ) / 2 (that is, wavelength λ ₁ and wavelength λ ₂ ). Therefore, the integral value P is expressed by the following equation.

A plurality of simulations in which the parameters of the image display device 30 were changed were carried out. The integral value P of the light emission under the strong interference condition, the weakening interference condition, and the non-interference condition in all the simulations was calculated. The ratio was calculated based on the brightness of light emission under non-interference conditions, and used as the rate of increase / decrease in light emission brightness due to interference.

5, 6 and 7 are charts showing the parameters of the image display device 30 changed in the simulation. 8, 9 and 10 are charts showing the results of calculations based on the above-mentioned theory of computation. In the simulation results shown in FIGS. 8 to 10, the simulations in which the result satisfying the condition 1 is obtained are referred to as Examples 1 to 17 in FIGS. 5 to 10, and the cases in which the condition 1 is not satisfied are referred to as Comparative Examples 1 to 10. It is called 35.

Here, each item shown in FIGS. 5 to 10 will be described.
<Total layer thickness>
The total thickness of the retardation expression layer 332 and the non-oriented layer 331 (corresponding to the thickness of the λ / 4 retardation layer 32) is shown.
<Non-oriented layer thickness>
The thickness of the non-oriented layer 331 is shown.
<Expression layer thickness>
The thickness of the phase difference expression layer 332 is shown.
<Ritaration>
The retardation of the λ / 4 retardation layer 32 (corresponding to the retardation of the retardation expression layer 332) is shown.
<Interference conditions>
The conditions in which the interference conditions at the peak wavelength λ _{0 are strengthened or weakened are shown.} "Strong" means a case where there is a strong condition, and "weak" means a case where there is a weakening condition.
<Full width at half maximum>
_{The lower limit wavelength λ 1} and the upper limit wavelength λ ₂ of the wavelength range that defines the full width at half maximum that defines the mountain-shaped region are shown. The full width at half maximum is the difference between _{λ 2} and λ _1.
<Extreme value of first interference spectrum>
It shows the wavelength at which the interference spectrum takes an extreme value under the strengthening condition.
Subscripts such as 1, 1a, and 2b are assigned younger numbers in order from 1 from the wavelength closest to _{the center (peak wavelength λ 0} ) of the mountain-shaped region M possessed by the emission spectrum of the image display unit 31. a is the short wavelength side and b is the long wavelength side. For example, in the case of "maximum 2b", it is the wavelength that takes the second maximum value on the long wavelength side counting from the center.
<Number of maximum values>
It shows the number of maximum values of the interference spectrum within the wavelength range that defines the full width at half maximum of the mountain-shaped region M.
<Second interference spectrum extremum>
It shows the wavelength at which the interference spectrum takes an extreme value under the weakening condition. The meanings of the subscripts such as 1, 1a and 2b are the same as in the case of the first interference spectrum extreme value.
<Number of local minimums>
It shows the number of minimum values of the interference spectrum within the wavelength range that defines the full width at half maximum of the mountain-shaped region M.
<Brightness increase / decrease rate>
The result of calculating the increase / decrease rate of the emission brightness due to interference is shown.

When the non-oriented layer thickness is 0, it corresponds to the case where the λ / 4 retardation layer 32 does not have the non-alignment layer 322 (that is, the λ / 4 retardation layer 32 is the retardation expression layer 321).

Under the condition that the rate of increase / decrease in brightness exceeds 100%, the emission brightness of the image display device increases without impairing the original display color, and the visibility is improved. From the results shown in FIGS. 8 to 10, the brightness increase / decrease rate exceeds 100% in Examples 1 to 17, while the brightness increase / decrease rate does not exceed 100% in Comparative Examples 1 to 35. Can be understood. Therefore, when the λ / 4 retardation layer 21 shown in FIG. 1 satisfies the above-mentioned condition 1, the emission brightness of the image display device 1 is increased without impairing the original display color, and the visibility is improved. Can be understood.

Here, the action and effect when the λ / 4 retardation layer 21 satisfies the above-mentioned condition 1 are specifically described by using a simulation. The above simulation may be used when designing the λ / 4 retardation layer 21. That is, for example, the thickness of the λ / 4 retardation layer 21 may be calculated based on the above simulation so that the brightness increase / decrease rate exceeds 100%.

Next, the results of the verification experiment will be explained. In the experiment, the optical laminate 20 shown in FIG. 1 was manufactured as follows.

[Formation of linearly polarized light layer]
A polarizing film (polarizer layer) having linear polarization characteristics and a saponified triacetyl cellulose (TAC) film (KC4UYTAC thickness 40 μm manufactured by Konica Minolta Co., Ltd.) are bonded together with a nip roll via an aqueous adhesive. It was. While maintaining the tension of the obtained laminate at 430 N / m, it was dried at 60 ° C. for 2 minutes to obtain a linearly polarized light layer (corresponding to the linearly polarized light layer 22) having a TAC film as a protective film on one side. The water-based adhesive is 100 parts of water, 3 parts of carboxyl group-modified polyvinyl alcohol (Kuraray Co., Ltd., "Kuraray Poval KL318"), and water-soluble polyamide epoxy resin (Taoka Chemical Industry Co., Ltd., "Smiley's Resin 650"). It was prepared by adding 1.5 parts of an aqueous solution having a solid content concentration of 30%.

The optical characteristics of the obtained linearly polarized light layer were measured. The measurement was carried out with a spectrophotometer (“V7100”, manufactured by JASCO Corporation) with the surface of the polarizing film of the linearly polarizing layer obtained above as an incident surface. The absorption axis of the polarizing film coincides with the stretching direction of polyvinyl alcohol, and the obtained linearly polarized light layer has a luminous efficiency-corrected single transmittance of 42.3%, a luminous efficiency-corrected polarization degree of 99.995%, and a single hue. a was −0.5 and the single hue b was 3.0.

[Preparation of composition for forming horizontal alignment film]
Five parts (weight average molecular weight: 30,000) of a photo-oriented material having the following structure and 95 parts of cyclopentanone (solvent) were mixed. The obtained mixture was stirred at 80 ° C. for 1 hour to obtain a composition for forming a horizontal alignment film.

[Preparation of composition for forming horizontally oriented liquid crystal cured film]
The following polymerizable liquid crystal compound α and polymerizable liquid crystal compound β were used to form a horizontally oriented liquid crystal cured film (A plate). The polymerizable liquid crystal compound α was produced by the method described in JP-A-2010-31223. Further, the polymerizable liquid crystal compound β was produced according to the method described in JP-A-2009-173893. The molecular structure of each is shown below.

[Polymerizable liquid crystal compound α]

[Polymerizable liquid crystal compound β]

The polymerizable liquid crystal compound α and the polymerizable liquid crystal compound β were mixed at a mass ratio of 87:13. 1.0 part of leveling agent (F-556; manufactured by DIC Corporation) and 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) as a polymerization initiator with respect to 100 parts of the obtained mixture. 6 parts of butane-1-one (Irgacure 369, manufactured by BASF Japan Ltd.) was added. Further, N-methyl-2-pyrrolidone (NMP) was added so that the solid content concentration was 13%, and the mixture was stirred at 80 ° C. for 1 hour to obtain a composition for forming a λ / 4 retardation layer.

[Formation of λ / 4 retardation layer]
Corona treatment was carried out on a cyclic olefin resin (COP) film (ZF-14-50) manufactured by Nippon Zeon Corporation. The corona treatment was performed using TEC-4AX manufactured by Ushio, Inc. The corona treatment was performed once under the conditions of an output of 0.78 kW and a processing speed of 10 m / min. The composition for forming a horizontal alignment film was applied to a COP film fixed on a glass substrate with a spin coater, and dried at 80 ° C. for 1 minute. The film is coated with a polarized UV irradiation device (“SPOT CURE SP-9”, manufactured by Ushio, Inc.), and the axial angle is 45 ° so that the ^{integrated light intensity at a wavelength of 313 nm is 100 mJ / cm 2.} Polarized UV exposure was performed at. The film thickness of the obtained horizontally aligned film was measured with an optical film thickness meter (manufactured by "F20" Filmometry) and found to be 100 nm. In the above coating, the dropping amount of the composition for forming a horizontal alignment film, the spinner rotation speed of the spin coater (“MS-B300”, manufactured by Mikasa Co., Ltd.) and the spinner rotation pattern are precisely adjusted, and the in-plane uniform and accurate The coating film thickness was obtained.

Subsequently, the composition for forming a λ / 4 retardation layer was applied to the horizontally aligned film using a spin coater (“MS-B300”, manufactured by Mikasa Sports Co., Ltd.), and dried at 120 ° C. for 1 minute. Irradiate the coating film with ultraviolet rays using a high-pressure mercury lamp (“Unicure VB-15201BY-A”, manufactured by Ushio, Inc.) (integrated light intensity at a wavelength of 365 nm under a nitrogen atmosphere: 500 mJ / cm ² ). As a result, a λ / 4 retardation layer (corresponding to the λ / 4 retardation layer 21) was formed.

An adhesive layer was laminated on the λ / 4 retardation layer. A film formed by a COP film, an alignment film, and a λ / 4 retardation layer was bonded to glass via the pressure-sensitive adhesive layer. The COP film was peeled off to obtain a sample for measuring retardation.

The retardation at a wavelength of 550 nm was measured with a phase difference measuring device (“KOBRA-WPR”, manufactured by Oji Measuring Instruments Co., Ltd.) and found to be 140.3 nm. Further, the layer thickness of the λ / 4 retardation layer was calculated from the above retardation and the refractive index and found to be 1900 nm.
In the above coating, the dropping amount of the composition for forming the λ / 4 retardation layer, the spinner rotation speed and spinner rotation pattern of the spin coater, the time from coating to drying, and the temperature in the drying furnace are precisely adjusted to be desired. In-plane uniform layer thickness and retardation were obtained.

An adhesive layer is laminated on the λ / 4 retardation layer side of the film formed by the COP film, the alignment film and the λ / 4 retardation layer, and the polarizing film side of the linear polarizing layer having the TAC film as a protective film is formed. A film formed by a COP film, an alignment film, a λ / 4 retardation layer, an adhesive layer, a polarizing film (polarizer layer), and a TAC film (protective film) was obtained by adhering through the pressure-sensitive adhesive layer. .. Further, the COP film of the film is peeled off, the pressure-sensitive adhesive layer is laminated on the alignment film surface which is the peeled surface, and the pressure-sensitive adhesive layer is laminated. "Body") was obtained. The portion of the first optical laminate other than the adhesive layer corresponds to the optical laminate 20 of the image display device 1 shown in FIG.

The transmission spectrum of the first optical laminate in the wavelength region of 400 nm to 500 nm was measured to obtain an interference spectrum. It was confirmed that the wavelengths were maximum values at 434 nm, 458 nm, and 484 nm, and minimum values were obtained at wavelengths of 446 nm and 470 nm, which were in agreement with the calculation results of Example 1.

An optical laminate made in the same manner except that the thickness of the λ / 4 retardation layer was 1955 nm, and the adhesive layer was laminated (hereinafter, referred to as "second optical laminate" for convenience of explanation). Got Further, the transmission spectrum of the second optical laminate in the region of wavelength 400 nm to 500 nm was measured to obtain an interference spectrum. It was confirmed that it had a maximum value at wavelengths of 446 nm and 470 nm and a minimum value at wavelengths of 434 nm, 458 nm and 484 nm, which were in agreement with the calculation results of Comparative Example 1.

In a smart phone with a built-in commercially available organic electroluminescence image display device (hereinafter referred to as "OLED image display device"), the glass and circular polarizing plate on the outermost surface on the viewing side are removed, and the OLED image display device possessed by the smart phone. The first optical laminate was laminated on (corresponding to the image display unit 10) via an adhesive layer. In that state, the display image of the OLED image device was displayed in blue, and the brightness of the light output from the first optical laminate was confirmed by the display evaluation system DMS803 (manufactured by Instrument Systems GmbH).
The first optical laminate except that the second optical laminate is laminated instead of the first optical laminate via an adhesive layer on the OLED image display device (corresponding to the image display unit 10) of the smart phone. The brightness of the light output from the second optical laminate was confirmed in the same manner as in the case of. As a result, the brightness of the emission peak of the smart phone with the OLED image display device in which the first optical laminate is laminated is increased by 5% as compared with the smart phone with the OLED image display in which the second optical laminate is laminated, and visually. I was able to strongly see the blue emission.

The present invention is not limited to the above embodiments and experimental examples, and is intended to include all modifications within the scope indicated by the claims, meaning and scope equivalent to the claims. To.

The image display unit uses an inorganic electroluminescence device having pixels that emit light independently, an electron emission display device (for example, an electric field emission display device (FED), a surface electric field emission display device (SED)), and electronic paper (electronic ink or an electrophoretic element). A display device), a plasma display device, a projection type display device (for example, a grating light valve (also referred to as GLV) display device, a display device having a digital micromirror device (also referred to as DMD), a piezoelectric ceramic display, or the like may be used.

An adhesive layer may be used instead of the adhesive layer.

The mountain-shaped region M is a region corresponding to any of the three primary colors, but it may be a region corresponding to another color (or wavelength range).

1 ... image display device, 10 ... image display unit, 10a ... image display surface, λ ₀ ... peak wavelength, 21 ... λ / 4 retardation layer, 22 ... linearly polarized light layer, 21a ... first surface, 21b ... second surface , 111 ... light emitting part, 211 ... retardation layer, 212 ... non-oriented layer, M ... mountain-shaped region.

Claims (10)

1. An image display unit that includes a light emitting unit and displays an image on the image display surface,
   The λ / 4 retardation layer provided on the image display surface and
   A linearly polarized light layer provided on the λ / 4 retardation layer and
   With
   The light from the light emitting portion has a mountain-shaped region including a light emitting peak and having a full width at half maximum of 60 nm or less.
   The λ / 4 retardation layer is configured to satisfy condition 1.
   Image display device.
   Condition 1: In the interference spectrum based on both sides in the thickness direction of the λ / 4 retardation layer, the number of maximum values within the wavelength range defining the full width at half maximum is one and the number of minimum values is two or less. is there.
2. The λ / 4 retardation layer is configured so as to further satisfy the condition 2.
   The image display device according to claim 1.
   Condition 2: The difference between the peak wavelength corresponding to the emission peak and the wavelength corresponding to the maximum value in the interference spectrum is 1/5 or less of the full width at half maximum.
3. The full width at half maximum is 20 nm.
   The peak wavelength corresponding to the emission peak is 458 ± 2 nm.
   The image display device according to claim 1 or 2.
4. The full width at half maximum is 40 nm.
   The peak wavelength corresponding to the emission peak is 523 ± 2 nm.
   The image display device according to claim 1 or 2.
5. The full width at half maximum is 40 nm.
   The peak wavelength corresponding to the emission peak is 530 ± 2 nm.
   The image display device according to claim 1 or 2.
6. The full width at half maximum is 50 nm.
   The peak wavelength corresponding to the emission peak is 626 ± 2 nm.
   The image display device according to claim 1 or 2.
7. The λ / 4 phase difference layer is a phase difference expression layer that gives λ / 4 phase difference to light.
   The image display device according to any one of claims 1 to 6.
8. The λ / 4 retardation layer is
   A phase difference expression layer that gives light a phase difference of λ / 4 and
   Non-oriented layer and
   Have,
   The image display device according to any one of claims 1 to 7.
9. The retardation expression layer and the non-oriented layer are laminated in close contact with each other.
   The difference in refractive index between the retardation layer and the non-oriented layer is zero.
   The image display device according to claim 8.
10. The λ / 4 retardation layer has a first surface in the thickness direction and a second surface opposite to the first surface.
    When the first surface and the second surface are interfaces among the refractive index differences at each of the plurality of interfaces through which the light output from the light emitting unit passes, including the first surface and the second surface. Refractive index difference is larger than other refractive index differences,
    The image display device according to any one of claims 1 to 9.

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