TWI865693B - Image display device - Google Patents

Abstract

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

An image display device according to one embodiment contains an image display unit that contains a light source and displays an image on the image display surface, a λ/4 retardation layer provided on the image display surface, and a linearly polarized light layer provided on the λ/4 retardation layer, wherein the light from the light source has a spectral region including an emission peak and a full width at half maximum of 60 nm or less, the λ/4 retardation layer is configured so that 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 in the interference spectrum based on both sides in the thickness direction of the λ/4 retardation layer.

Description

Image display device

The present invention relates to an image display device.

As an image display device, a device is known that has an image display unit including a light-emitting unit, a λ/4 phase difference layer, and a linear polarization layer in order from the back side to the front side (see, for example, Patent Document 1). Examples of the above-mentioned image display unit include flat panel display devices (such as thin liquid crystal display devices, thin organic electroluminescent image display devices, etc.).

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2019-79053

When a picture display device displays a color picture, for example, a light-emitting unit that outputs the three primary colors (red, blue, and green) of light is used. Due to the influence of the materials used to output each color, for example, even if the light-emitting units (or light-emitting elements) that output red, blue, and green are driven under the same conditions, the intensity of light of a specific color may become weaker, making it difficult to display the color that was originally intended to be displayed. If the light-emitting unit (light-emitting element) that outputs the above-mentioned specific color is used at high brightness to eliminate such an undesirable situation, the life of the light-emitting unit will be shortened, resulting in a shortened product life of the picture display device.

Therefore, the purpose of the present invention is to provide an image display device that ensures the product life of the image display device and can display images in the desired color state.

The image display device of the present invention comprises: an image display unit including a light-emitting unit and displaying an image on an image display surface; a λ/4 phase difference layer disposed on the image display surface; and a linear polarization layer disposed on the λ/4 phase difference layer; wherein the light from the light-emitting unit includes a mountain-shaped region with a luminescence peak and a half-maximum full width of less than 60nm, and the λ/4 phase difference layer is constructed in a manner that satisfies condition 1.

Condition 1: In the interference spectrum of both surfaces in the thickness direction of the λ/4 phase difference layer, the number of maximum values in the wavelength range defining the full width at half maximum is 1 and the number of minimum values is 2 or less.

With the above configuration, even if the intensity of the light output from the light-emitting portion and having the light-emitting spectrum including the mountain-shaped region becomes weak, the color corresponding to the mountain-shaped region can be enhanced based on the interference of the two surfaces of the λ/4 phase difference layer. Therefore, for example, if the intensity of one of the three primary colors becomes weak, the color can be enhanced by the interference effect of the λ/4 phase difference layer, so that the image can be displayed in the desired color state. Furthermore, the enhancement of the color by the interference effect of the λ/4 phase difference layer can suppress the degradation of the light-emitting portion. As a result, the product life of the image display device can also be ensured.

The above-mentioned λ/4 phase difference layer can also be further constructed in a manner that satisfies condition 2.

Condition 2: The difference between the peak wavelength corresponding to the above-mentioned luminescence peak and the wavelength corresponding to the above-mentioned maximum value of the above-mentioned interference spectrum is less than 1/5 of the above-mentioned full width at half maximum.

The above-mentioned full width at half maximum is 20nm, and the peak wavelength corresponding to the above-mentioned luminescence peak can be 458±2nm.

The above-mentioned full width at half maximum is 40nm, and the peak wavelength corresponding to the above-mentioned luminescence peak can be 523±2nm.

The above-mentioned full width at half maximum is 40nm, and the peak wavelength corresponding to the above-mentioned luminescence peak can be 530±2nm.

The above-mentioned full width at half maximum is 50nm, and the peak wavelength corresponding to the above-mentioned luminescence peak can be 626±2nm.

The above-mentioned λ/4 phase difference layer can be a phase difference display layer that imparts a λ/4 phase difference to light.

The above-mentioned λ/4 phase difference layer may have a phase difference display layer that imparts a λ/4 phase difference to light and a non-aligned layer. In this case, the thickness of the λ/4 phase difference layer can be adjusted by the non-aligned layer.

The phase difference display layer and the non-aligned layer are closely stacked with each other, and the refractive index difference between the phase difference display layer and the non-aligned layer can be zero. In this case, substantially no reflection is generated at the interface between the phase difference display layer and the non-aligned layer.

The λ/4 phase difference layer has a first surface and a second surface opposite to the first surface in the thickness direction. Among the refractive index differences of the multiple interfaces including the first surface and the second surface through which the light output from the light-emitting portion passes, the refractive index difference when the first surface and the second surface are interfaces may be greater than the other refractive index differences.

In this case, in the spectrum of light output from the image display device, interference based on reflections on the first surface and the second surface becomes dominant, and the color corresponding to the mountain-shaped area is easily enhanced by utilizing the interference of the λ/4 phase difference layer.

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

1,30: Image display device

2a, 2b, 32a, 32b: Adhesive layer

10,31: Image display unit

10a: Image display surface

11: Light source

12: Image display layer

20: Optical laminates

21,33:λ/4 phase difference layer

21a: Page 1

21b: Page 2

22,34: Linear polarizing layer

111: Luminous Department

211,332: Phase difference display layer

212,331: No alignment layer

A: Light path

B: Light path

M: Yamagata area

λ ₀ : Peak wavelength

λ ₁ : Lower limit wavelength

λ ₂ : Upper wavelength

FIG1 is a schematic diagram showing the schematic structure of an image display device according to an embodiment.

Figure 2 is a conceptual diagram of the mountain-shaped area of the luminous spectrum of light output from the light-emitting unit.

Figure 3 is a schematic diagram showing the general structure of the simulation.

Figure 4 is a schematic diagram illustrating the luminescence spectrum used in the simulation.

Figure 5 is a graph showing the parameters used in the simulation.

Figure 6 is a graph showing the parameters used in the simulation.

Figure 7 is a graph showing the parameters used in the simulation.

Figure 8 is a graph showing the simulation results.

Figure 9 is a graph showing the simulation results.

Figure 10 is a graph showing the simulation results.

Below, the implementation of the present invention is described with reference to the drawings. The same components are given the same symbols and repeated descriptions are omitted. The size ratios in the drawings may not be the same as the sizes in the description.

FIG1 is a schematic diagram showing a schematic structure of an image display device 1 according to an embodiment. The image display device 1 has an image display unit 10 and an optical multilayer body 20. The optical multilayer body 20 is stacked on the image display unit 10. Since the image is observed from the optical multilayer body 20, in the image display device 1, the optical multilayer body 20 is called the front side and the image display unit 10 is called the back side.

[Image display unit]

The image display unit 10 is a device for outputting images. The image display unit 10 has an image display surface 10a for displaying (or outputting) images. 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 where no optical compensation components are included on the image display surface 10a.

As shown in FIG1 , an image display unit 10 of an embodiment includes a light source unit 11 and an image display layer 12. An example of the image display unit 10 including the light source unit 11 and the image display layer 12 separated from the light source unit 11 is a liquid crystal display device. Examples of liquid crystal display devices include any of a transmissive liquid crystal display device and a semi-transmissive liquid crystal display device.

[Light source]

The light source unit 11 supplies illumination light (e.g., backlight) to the image display layer 12. The light source unit 11 has a light-emitting unit 111. As shown in FIG2 , the light-emitting unit 111 outputs light having a mountain-shaped region M with a luminescence peak and a full width at half maximum of less than 60 nm. FIG2 is a conceptual diagram of the mountain-shaped region M of the luminescence spectrum of the light output from the light-emitting unit 111.

For the sake of convenience, the wavelength of the luminescence peak corresponding to the mountain-shaped region M is referred to as the peak wavelength λ ₀ . In the wavelength range that defines the full width at half maximum of the mountain-shaped region M, the lower limit wavelength (the wavelength on the short wavelength side of the above wavelength range) is referred to as the wavelength λ ₁ , and the upper limit wavelength (the wavelength on the long wavelength side of the above wavelength range) is referred to as the wavelength λ ₂ .

An example of the light-emitting section 111 is an LED (light-emitting diode). In the case where the light-emitting section 111 is a point light source such as an LED, as shown schematically in FIG1 , the light source section 11 has a plurality of light-emitting sections 111. The light-emitting section 111 can output light including, for example, three primary colors (red, green, and blue). An example of such a light-emitting section 111 is, for example, a white LED. In the case where the light-emitting section 111 outputs light including three primary colors, the luminous spectrum of the light output from the light-emitting section 111 has mountain-shaped regions corresponding to the colors of the three primary colors. In this case, at least one of the mountain-shaped regions of red, green, and blue satisfies the condition of the mountain-shaped region M described above. Alternatively, the light source section 11 may have a light-emitting section 111 that outputs blue, a light-emitting section 111 that outputs green, and a light-emitting section 111 that outputs red. In this case, the luminous spectrum of the light output by at least one of the light-emitting units 111 for blue, green, and red has the mountain-shaped region M described above.

As an example of the mountain-shaped region M, according to the combination of the peak wavelength λ ₀ and the full width at half maximum, there can be the first to fourth mountain-shaped regions shown in Table 1. Table 1 also shows the colors corresponding to the first to fourth mountain-shaped regions.

[Image display layer]

The image display layer 12 has a plurality of pixels and is a layer that forms an image by controlling the penetration 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 embodiment 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.

Regarding the image display unit 10 of one embodiment, it is also possible to have a self-luminous image display layer 12 that allows the pixels of the image display layer 12 to function as the light-emitting unit 111. In this case, as shown in FIG1, the light source unit 11 separated from the image display layer 12 is not required. An example of a self-luminous image display layer 12 is an organic electroluminescent (organic EL) image display element. Even if the image display layer 12 is a self-luminous layer, the example of the mountain-shaped area M of the luminous spectrum of the light output by the pixel (light-emitting unit) is the same as the case where the light source unit 11 and the image display layer 12 are separated as shown in FIG1.

[Optical laminate]

The optical multilayer 20 has a λ/4 phase difference layer 21 and a linear polarization layer 22. The optical multilayer 20 is a component for optically compensating the image displayed on the image display surface 10a. The optical multilayer 20 functions as a circular polarizer or an elliptical polarizer, for example.

[λ/4 phase difference layer]

The λ/4 phase difference layer 21 is an optical functional layer that imparts a phase difference of λ/4 to light passing through (or penetrating) the λ/4 phase difference layer 21. An example of the thickness of the λ/4 phase difference layer 21 is 0.5μm to 5.0μm. An example of the refractive index of the λ/4 phase difference layer 21 is 1.50 to 1.70. The λ/4 phase difference layer 21 is attached to the image display unit 10 via the adhesive layer 2a.

The adhesive layer 2a can be composed of an adhesive composition with (meth) acrylic, rubber, urethane, ester, silicone, and polyvinyl ether resins as the main components. Among them, the adhesive composition with (meth) acrylic resin having excellent transparency, weather resistance, heat resistance, etc. as the base polymer is suitable. The adhesive composition can be active energy ray curing type or heat curing type. The thickness of the adhesive layer 2a is usually 3μm to 30μm, and preferably 3μm to 25μm. The refractive index of the adhesive layer 2a is 1.40 to 1.55.

[Linear polarizing layer]

The linear polarizing layer 22 is an optical functional layer having linear polarizing properties. The linear polarizing layer 22 is, for example, a linear polarizing plate. The linear polarizing layer 22 has a polarizing film (polarizing sublayer) having linear polarizing properties and a protective film for protecting the polarizing film. The thickness of the linear polarizing layer 22 is, for example, 12 μm to 140 μm.

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

Examples of resin films used as polarizing films include polyvinyl alcohol (hereinafter referred to as "PVA") resin films, polyvinyl acetate resin films, ethylene/vinyl acetate resin films, polyamide resin films, and polyester resin films. PVA resin films, especially PVA films, are usually used from the viewpoint of adsorption and orientation of dichroic dyes.

An example of the thickness of the polarizing film is 2.0 μm to 40 μm. An example of the refractive index of the 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 (such as a triacetyl cellulose (hereinafter also referred to as "TAC") film), a glass cover or a glass film. The thickness of the protective film is, for example, 10 μm to 100 μm. The refractive index of the protective film is, for example, 1.40 to 1.70.

The linear polarizing layer 22 may have two protective films on the polarizing film, for example. In this case, the protective films are laminated on both sides of the polarizing film. The materials, thicknesses and refractive indices of the two protective films are as described above. The materials, thicknesses and refractive indices of the two protective films may be the same or different.

The linear polarizing layer 22 can be manufactured by preparing long strips of components, bonding the components in a roll-to-roll manner, and then cutting them into a predetermined shape, or by cutting the components into a predetermined shape and then bonding them.

The linear polarization layer 22 is bonded to the λ/4 phase difference layer 21 via the adhesive layer 2b. The adhesive layer 2b is the same as the adhesive layer 2a.

The linear polarizing layer 22 is a polarizing film with a protective film, and the linear polarizing layer 22 is usually bonded to the λ/4 phase difference layer 21 by placing the polarizing film close to the λ/4 phase difference layer 21.

The above-mentioned image display device 1 is manufactured, for example, in the following manner.

The λ/4 phase difference layer 21 and the linear polarization layer 22 are manufactured separately. Then, the optical multilayer 20 is formed by bonding them. Then, the optical multilayer 20 is bonded to the image display unit 10 via the adhesive layer 2a to manufacture the image display device 1. When bonding the optical multilayer 20 to the image display unit 10, the λ/4 phase difference layer 21 is arranged close to the image display unit 10.

In an image display device 1 of an embodiment, for example, among the refractive index differences of a plurality of interfaces through which light output from the light-emitting portion 111 passes, the refractive index difference when the first surface 21a and the second surface 21b are interfaces is greater than the other refractive index differences. The so-called refractive index difference at the interface refers to the refractive index difference on both sides of the interface. Such a refractive index difference can be achieved, for example, by adjusting the materials constituting each layer.

Next, the λ/4 phase difference layer 21 is further described. As shown in FIG. 1 , the λ/4 phase difference layer 21 has a phase difference display layer 211 and a non-aligned layer 212.

The phase difference display layer 211 is a layer that functions as the λ/4 phase difference layer 21 only through the phase difference display layer 211. The phase difference display layer 211 can be formed by a known material and formation method used for a 1/4 wavelength plate, for example.

The phase difference display layer 211 may be a stretched resin film obtained by stretching the resin film. The phase difference display layer 211 may be a layer formed by, for example, a cured product of a polymerizable liquid crystal compound that is cured in a state of being aligned in a single direction. As the polymerizable liquid crystal compound, for example, a compound showing reverse dispersion is suitable.

Regarding the types of the above-mentioned polymerizable liquid crystal compounds, although there are no special restrictions, they can be classified into rod-shaped types (rod-shaped liquid crystal compounds) and disc-shaped types (disc-shaped liquid crystal compounds, disc-shaped liquid crystal compounds) based on their shapes. Furthermore, there are low-molecular types and high-molecular types. Furthermore, the so-called polymer generally refers to those with a polymerization degree of 100 or more (refer to "Polymer Physics and Phase Transfer Dynamics, written by Masao Doi, Iwanami Shoten, 1992").

The phase difference display layer 211 can use any polymerizable liquid crystal compound. Furthermore, two or more rod-shaped liquid crystal compounds, two or more disc-shaped liquid crystal compounds, or a mixture of rod-shaped liquid crystal compounds and disc-shaped liquid crystal compounds can also be used.

As a rod-shaped liquid crystal compound, for example, the compound described in claim 1 of Japanese Patent Publication No. 11-513019 or paragraphs [0026] to [0098] of Japanese Patent Publication No. 2005-289980 can be suitably used. As a disc-shaped liquid crystal compound, for example, the compound described in paragraphs [0020] to [0067] of Japanese Patent Publication No. 2007-108732 or paragraphs [0013] to [0108] of Japanese Patent Publication No. 2010-244038 can be suitably used.

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

The polymerizable liquid crystal compound has a polymerizable group that can undergo a polymerization reaction. As the polymerizable group, a functional group that can undergo an addition polymerization reaction, such as a polymerizable ethylenic unsaturated group and a cyclic polymerizable group, is ideal. More specifically, as the polymerizable group, for example, a (meth)acryl group, a vinyl group, a styrene group, an allyl group, etc. are examples. Among them, a (meth)acryl group is ideal. Furthermore, the so-called (meth)acryl group refers to a concept that includes both a methacryl group and an acryl group.

The phase difference display layer 211 has, for example, an A plate. The A plate can be formed, for example, from the above-mentioned polymerizable liquid crystal compound. In this case, the A plate is a horizontally aligned liquid crystal cured film. The phase difference display layer 211 can further have a horizontally aligned film for the A plate. The phase difference display layer 211 as a laminate of the horizontally aligned film and the A plate is manufactured, for example, by sequentially forming a horizontally aligned film and an A plate on a supporting substrate such as a resin film, and then peeling off the supporting substrate.

In the case where the phase difference display layer 211 is a laminate, each layer constituting the phase difference display layer 211 is formed in a manner having substantially the same refractive index to avoid reflection at the interface between the layers. This can be achieved by selecting the materials of each layer so that each layer has the same refractive index, or by adding appropriate additives to the materials of each layer to adjust the refractive index.

The non-aligned layer 212 is closely laminated on the phase difference display layer 211. The non-aligned layer 212 is arranged in the λ/4 phase difference layer 21 to be close to the image display part 10. The non-aligned layer 212 is a layer used to adjust the thickness of the λ/4 phase difference layer 21. The in-plane phase difference of the non-aligned layer 212 is less than 0.1nm (that is, substantially zero), and it is a layer that does not impart a phase difference to light. The non-aligned layer 212 has a refractive index that is substantially the same as that of the phase difference display layer 211 to avoid reflection at the interface between the non-aligned layer 212 and the phase difference display layer 211. For example, the refractive index difference on both sides of the interface between the non-aligned layer 212 and the phase difference display layer 211 is less than 0.02 (substantially zero). The non-aligned layer 212 is, for example, a layer formed by a cured material cured by an ultraviolet (UV) adhesive. The above-mentioned UV adhesive may also contain thiophene, thiourea, carbazole, fluorene, etc. as additives. Such additives can be used to adjust the refractive index.

The λ/4 phase difference layer 21 may also be a layer formed only by the phase difference display layer 211 (i.e., it does not have a structure without an alignment layer 212).

The λ/4 phase difference layer 21 is configured to satisfy the following condition 1.

[Condition 1]

In the interference spectra of the two surfaces (the first surface 21a and the second surface 21b) in the thickness direction of the λ/4 phase difference layer 21, the number of maximum values within the wavelength range (above λ ₁ and below λ ₂ ) defining the half-maximum full width of the mountain-shaped region M is 1 and the number of minimum values is 2 or less.

In the configuration of the image display device 1 including the λ/4 phase difference layer 21, when light of a wavelength range including the half-width at half maximum defining the mountain-shaped region M (for example, light of a wavelength of 400nm to 500nm in the case where the mountain-shaped region M corresponds to blue) is incident on the λ/4 phase difference layer 21, the above-mentioned interference spectrum is the interference spectrum generated by reflection from the first surface 21a (back side interface) and the second surface 21b (front side interface) of the λ/4 phase difference layer 21.

In the case where the image display unit 10 has a light-emitting unit 111 that outputs three primary colors (red, green, and blue), or has a light-emitting unit 111 that corresponds to the three primary colors, it is assumed that there is a mountain-shaped area M corresponding to each color (red, green, and blue). In this case, the mountain-shaped area M of condition 1 is a mountain-shaped area M corresponding to one of red, green, and blue. For example, it is a mountain-shaped area corresponding to blue. In this case, it can also be the first mountain-shaped area shown in Table 1.

In the case where the λ/4 phase difference layer 21 has no alignment layer 212, the first surface 21a is the surface of the phase difference display layer 211 opposite to the alignment layer 212 (in other words, the surface on the image display unit 10 side), and the second surface 21b is the surface of the phase difference display layer 211 opposite to the alignment layer 212 (in other words, the surface on the linear polarization layer 22 side). In the case where the λ/4 phase difference layer 21 does not have no alignment layer 212, the first surface 21a is the surface of the phase difference display layer 211 on the image display unit 10 side, and the second surface 21b is the surface of the phase difference display layer 211 on the linear polarization layer 22 side.

The λ/4 phase difference layer 21 can also be further configured in a manner that satisfies the following condition 2.

[Condition 2]

The difference between the wavelength corresponding to the maximum value of the interference spectrum and the peak wavelength λ ₀ is less than 1/5 of the full width at half maximum of the mountain-shaped region M.

Condition 1 can be achieved by adjusting the thickness and refractive index of the λ/4 phase difference layer 21. For example, if the refractive index of the λ/4 phase difference layer 21 is increased, the thickness of the λ/4 phase difference layer 21 can be reduced, so it is easy to meet the above condition 1. The same is true for condition 2.

The maximum value of the interference spectrum recorded in condition 1 is caused by interference between the interfaces of the λ/4 phase difference layer 21 (between the first surface 21a and the second surface 21b). When the distance between the interfaces (the thickness of the λ/4 phase difference layer 21) changes slightly, the wavelength of the maximum value will change significantly. For example, when the thickness is 1.890μm, there is a maximum value at 455nm. When the thickness changes only slightly (±0.050μm) to 1.940μm or 1.840μm, the peak wavelength of the maximum value of the interference spectrum deviates from 455nm and becomes 442nm or 468nm. On the contrary, 455nm becomes a very small peak.

Therefore, it is ideal to use, for example, precision coating (e.g., coating method with a wet film thickness accuracy of tens of nanometers) to manufacture the λ/4 phase difference layer 21. An example of the precision coating method is described below.

(λ/4 phase difference layer 21)

Coating with a wet film thickness accuracy of tens of nanometers can be achieved by slit coating, rotary coating, gravure coating, etc. In any method, it is ideal to use a coating liquid with low solid content concentration and low viscosity, stabilize the temperature and concentration of the coating liquid, shorten the time from the coating step to the drying step, perform the drying step under a stable airflow, and irradiate the active energy ray with the optimal irradiation amount.

Furthermore, by accurately feeding back the control items of each coating method, the film thickness and phase difference of the obtained coating dried product can further achieve precise coating. When using the slit coating method, the discharge amount from the die lip, the lip shape, and the distance between the die lip and the coating target substrate are important control items. When using the rotary coating method, the airflow stabilization of the coating environment, the rotation speed of the rotor, and the dripping amount are important control items.

When using the gravure coating method, the speed of the gravure roller and the speed ratio of the gravure roller to the back pressure roller are important control items.

When the λ/4 phase difference layer 21 is the phase difference display layer 211 (i.e., when there is no non-aligned layer 212), the phase difference display layer 211 can be manufactured using the above-mentioned precision coating.

In the case where the λ/4 phase difference layer 21 has a non-aligned layer 212, the thickness can be adjusted by the non-aligned layer 212. In this case, the phase difference display layer 211 is formed by, for example, the same method as the formation of the known 1/4 wavelength plate, and the non-aligned layer 212 is formed by the above-mentioned precision coating.

The following describes an example of forming a non-aligned layer 212 with a refractive index of about 1.61 by precisely controlling the thickness. In this case, a bisphenol-a acrylate monomer (OGSOLEA-0200 manufactured by Osaka Gas Chemical Co., Ltd.) and a photoradical polymerization initiator (IRGACURE907 manufactured by BASF) are dissolved in a toluene solution at a mass ratio of 97:3 to prepare a solution with a solid content concentration of 5% to obtain a coating liquid, which is then applied to the phase difference display layer 211 using a rotary coater, and then dried and UV-irradiated to obtain a non-aligned layer 212 with a precisely controlled thickness.

As mentioned above, the wavelength of the maximum value of the interference spectrum of condition 1 depends on the distance between the interfaces. Therefore, the thickness of the λ/4 phase difference layer 21 can be adjusted, and the above-mentioned non-aligned layer 212 plays the role of an interference control layer.

In the above-mentioned image display device 1, the λ/4 phase difference layer 21 satisfies the above-mentioned condition 1. Thus, among the light outputted from the light-emitting unit 111 of the image display unit 10, the light corresponding to the mountain-shaped area M is strongly displayed in color from the image display device 1.

Thus, for example, even if the intensity of any one of the three primary colors is lower than that of the other colors, the reduced intensity of the color relative to the other colors can be compensated by the interference effect on both sides of the λ/4 phase difference layer 21. As a result, color rendering (desired color state) can be achieved naturally. Furthermore, in order to eliminate the above-mentioned reduced intensity state, it is not necessary to increase the brightness of the light-emitting portion 111 of the color with low output intensity, so the degradation of the light-emitting portion 111 can be suppressed. As a result, the product life of the image display device 1 can also be ensured.

For example, blue luminescent materials have compound stability issues, and it is known that using them at high brightness will damage the life of the luminescent element (luminescent part). This is particularly prominent in the case of organic luminescent elements, and compounds containing styrylamine groups, which are often used as blue luminescent compounds, are particularly applicable.

Even in such a case, by setting the mountain-shaped area M that satisfies condition 1 of the above-mentioned λ/4 phase difference layer 21 as the area corresponding to blue, the interference effect of the two surfaces of the λ/4 phase difference layer 21 is utilized to make the blue color more intense than, for example, green and red. As a result, the luminous intensity of the blue light can be weakened and the life of the light-emitting portion 111 can be extended while maintaining natural color rendering.

The λ/4 phase difference layer 21 further satisfies the condition 2, because it can reduce the destructive effect caused by interference, and it is further easier to achieve the desired color state. In order to reduce the destructive effect caused by interference, it is more ideal to make the wavelength of the maximum value corresponding to the interference spectrum the same as the peak wavelength λ ₀ .

In one embodiment, among the refractive index differences of the multiple interfaces through which the light output from the light-emitting portion 111 passes, the refractive index difference when the first surface 21a and the second surface 21b are interfaces is greater than the other refractive index differences. In this case, the interference component contained in the spectrum of the light output from the linear polarization layer 22 has a large influence on the interference based on the two surfaces (the back side interface and the front side interface) of the λ/4 phase difference layer 21. Therefore, the above-mentioned light enhancement effect caused by the interference action of the λ/4 phase difference layer 21 is more effective.

Then, by satisfying condition 1, the points corresponding to the color of the mountain-shaped area M can be enhanced and verified by simulation. Explain the verification simulation.

In the simulation, the image display device 30 shown in FIG. 3 is used as a simulation model. The image display device 30 includes an image display portion 31, an adhesive layer 32a, a λ/4 phase difference layer 33, an adhesive layer 32b, and a linear polarization layer 34. The adhesive layer 32a, the λ/4 phase difference layer 33, the adhesive layer 32b, and the linear polarization layer 34 are sequentially stacked on the image display portion 31. The λ/4 phase difference layer 33 has a non-aligned layer 331 on the side of the adhesive layer 32a, and has a phase difference display layer 332 on the non-aligned layer 331. The image display device 30 is arranged in the air.

The image display part 31, adhesive layer 32a, λ/4 phase difference layer 33, adhesive layer 32b, linear polarization layer 34, non-aligned layer 331 and phase difference display layer 332 are respectively models of the image display part 10, adhesive layer 2a, λ/4 phase difference layer 21, adhesive layer 2b, linear polarization layer 22, non-aligned layer 212 and phase difference display layer 211.

In the description of the simulation, the refractive indexes of the image display section 31, the non-aligned layer 212, the phase difference display layer 211, and the linear polarization layer 34 are referred to as _nG , _nR , _nR , and _nP , respectively. The refractive index _nG of the image display section 31 is the refractive index of the portion adjacent to the adhesive layer 32a (i.e., the portion in contact with the side of the image display section 31 in the interface between the image display section 31 and the adhesive layer 32a). It is assumed that the refractive indexes of the non-aligned layer 212 and the phase difference display layer 211 are the same. Therefore, the refractive index of the λ/4 phase difference layer 33 is also _nR . The adhesive layer 32a and the adhesive layer 32b also have the same refractive index, which is referred to as n _PSA .

In the simulation implemented, n _G , n _PSA , n _R , and n _P use the values in Table 2. The refractive index shown in Table 2 is the refractive index at a wavelength of 550 nm. The values of the refractive indices shown in Table 2 correspond to the refractive indices of the materials used in each layer of the image display device 1. The refractive index n _G of the image display portion 31 is the refractive index of glass. This is because the portion of the image display portion 31 that is in contact with the adhesive layer 32a is mostly glass, for example, as a sealing material (or protective member). Table 2 also shows the refractive index of the air on the outside of the linear polarizing layer 34.

In the simulation, the mountain-shaped area M output from the light-emitting unit 111 is assumed to be light output from the image display unit 31. The following describes the conditions and calculation theory used in the simulation.

〈Full width at half maximum of interference spectrum〉

As shown in Fig. 4, the luminous spectrum of the light output from the image display unit 31 is set to a spectrum having a single peak continuous function f(λ) of wavelength λ and a maximum value f(λ ₀ ). The two wavelengths λ satisfying f(λ ₀ )/2 are set to wavelengths λ ₁ and λ ₂ (where λ ₂ >λ ₁ ) as in the case of Fig. 1 . In this case, the full width at half maximum of the mountain-shaped region M represented by the single peak continuous function f(λ) is calculated by λ ₂ -λ ₁ .

〈Extrema of interference spectrum〉

Interference spectrum is a continuous trigonometric function of the maximum values obtained from interference, from short wavelength to long wavelength, in the order of maximum, minimum and maximum or minimum, maximum and minimum.

As shown in Figure 3, the optical path that sequentially reflects the front side interface (equivalent to the second surface 21b) and the back side interface (equivalent to the first surface 21a) of the λ/4 phase difference layer 33 and advances is called optical path A, and the optical path that passes through and advances without being reflected at any interface is called optical path B. The interference generated by the difference between optical path A and optical path B, the constructive condition and the destructive condition are shown as follows.

Mutual growth conditions:

△L≡m λ but m=1,2,3‧‧‧

Cancellation conditions:

△L≡(m+1/2) λbut m=0,1,2‧‧‧

In the above constructive and destructive conditions, △L is the optical path difference between optical path A and optical path B, as expressed by the following formula.

△ L =2 n _R d _R

Here, d _R is the thickness of the λ/4 phase difference layer 33 , and is the sum of the thicknesses of the non-aligned layer 212 and the phase difference display layer 211 .

Based on the above-mentioned constructive and destructive conditions, the wavelength λ _in corresponding to the maximum value and the wavelength λ _out corresponding to the minimum value are expressed as follows.

In this simulation, wavelength dispersion is not considered in the λ/4 phase difference layer 33. However, if there is wavelength dispersion, for example, the wavelength λ _k at which the maximum and minimum values are obtained is calculated using the refractive index n _R (λ _k ) corresponding to each wavelength.

〈Intensity of interference spectrum〉

The reflectivity _r1 to _r4 of the interface between each layer shown in FIG3 is expressed as follows using the refractive index of each layer. Reflectivity _r1 is the reflectivity of the interface between the image display portion 31 and the adhesive layer 32a. Reflectivity _r2 is the reflectivity of the interface between the λ/4 phase difference layer 33 and the adhesive layer 32a and the interface between the λ/4 phase difference layer 33 and the adhesive layer 32b. Reflectivity _r3 is the reflectivity of the interface between the adhesive layer 32b and the linear polarization layer 34. Reflectivity _r4 is the reflectivity of the interface between the linear polarization layer 34 and air.

When the photoelectric field intensity of light output from the inside of the image display unit 10 is _E0 , the photoelectric field energies _{EA and EB} of the optical path A and the optical path B shown in FIG3 are expressed as follows.

E _A = E ₀ ×(1- r ₁ )×(1- r ₂ )× r ₂ × r ₂ ×(1- r ₂ )×(1- r ₃ )×(1- r ₄ )

E _B = E ₀ ×(1- r ₁ )×(1- r ₂ )×(1- r ₂ )×(1- r ₃ )×(1- r ₄ )

The photoelectric field intensity under constructive conditions is _Ein and the photoelectric field intensity under destructive conditions is _Eout as shown in the following formula.

The intensity of the photoelectric field under the condition of no interference is _En, which is expressed as follows.

E _n = E _B

〈Evaluation Method〉

The brightness of blue, green, and red emitted from the image display device 30 is proportional to the integral value of the luminescence spectrum S(λ). The intensity amplitude spectrum (equivalent to the interference spectrum) E(λ) caused by the interference of the two sides (the back side interface and the front side interface) of the λ/4 phase difference layer 33 is multiplied by the luminescence spectrum S(λ) to obtain the luminescence interference spectrum E(λ)×S(λ). The integral value P of the luminescence interference spectrum is used to evaluate the luminescence brightness under the constructive interference condition and the destructive interference condition.

The range of the integrated wavelength λ is 2 wavelengths (i.e. wavelength λ ₁ and wavelength λ ₂ ) that satisfy f(λ ₀ )/2. Therefore, the integrated value P is expressed as follows.

Perform multiple simulations after changing the parameters of the image display device 30. Calculate the integral value P of the luminescence under the constructive interference condition, destructive interference condition and non-interference condition of all simulations. Calculate the ratio based on the brightness of the luminescence under the non-interference condition as the increase or decrease rate of the luminescence brightness caused by interference.

Figures 5, 6 and 7 are graphs showing the parameters of the image display device 30 that have been changed in the simulation. Figures 8, 9 and 10 are graphs showing the results calculated based on the above calculation theory. Among the simulation results shown in Figures 8 to 10, the simulations that meet condition 1 are referred to as embodiments 1 to 17 in Figures 5 to 10, and the simulations that do not meet condition 1 are referred to as comparative examples 1 to 35.

Here, the items shown in Figures 5 to 10 are explained.

〈Total layer thickness〉

Indicates the total thickness of the phase difference display layer 332 and the non-aligned layer 331 (equivalent to the thickness of the λ/4 phase difference layer 33).

〈Non-aligned layer thickness〉

Indicates the thickness of the non-aligned layer 331.

〈Appearance thickness〉

Indicates the thickness of the phase difference display layer 332.

<delay>

Indicates the delay of the λ/4 phase difference layer 33 (equivalent to the delay of the phase difference display layer 332).

<Interference conditions>

The interference condition at the peak wavelength λ ₀ shows either a constructive condition or a destructive condition. "Strong" refers to the case of a constructive condition, and "weak" refers to the case of a destructive condition.

〈Half peak, full width〉

Indicates 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 of the mountain-shaped region. The full width at half maximum is the difference between λ ₁ and λ ₂ .

〈1st interference spectrum extreme value〉

The wavelength at which the interference spectrum reaches its maximum value when constructive conditions are present.

The labels such as 1, 1a, 2b are assigned small numbers starting from 1 in order from the wavelength near the center (peak wavelength λ ₀ ) of the mountain-shaped area M of the light spectrum of the image display unit 31. a is the short wavelength side, and b is the long wavelength side. For example, "Maximum 2b" is the wavelength that is the second from the center and has a maximum value on the long wavelength side.

〈Number of extreme values〉

Indicates 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 Extreme〉

The wavelength at which the interference spectrum reaches its maximum value when destructive conditions are met.

The meanings of the labels 1, 1a, 2b, etc. are the same as those of the first interference spectrum extreme value.

〈Number of minimum values〉

Indicates the number of minima 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〉

Indicates the result of calculating the rate of increase or decrease of luminous brightness caused by interference.

When the thickness of the non-aligned layer is 0, it is equivalent to the situation that the λ/4 phase difference layer 33 does not have the non-aligned layer 331 (that is, the λ/4 phase difference layer 33 is the phase difference display layer 332).

Under the condition that the brightness increase/decrease rate exceeds 100%, the brightness of the image display device is increased without damaging the original display color, thereby improving the recognition. From the results shown in Figures 8 to 10, it can be understood that in Examples 1 to 17, the brightness increase/decrease rate exceeds 100%, while on the other hand, the brightness increase/decrease rate of Comparative Examples 1 to 35 does not exceed 100%. Therefore, the λ/4 phase difference layer 21 shown in Figure 1 increases the brightness of the image display device without damaging the original display color by satisfying the above-mentioned condition 1, thereby improving the recognition.

Here, simulation is used to specifically explain the effect of the λ/4 phase difference layer 21 satisfying the above condition 1. The above simulation can also be used when designing the λ/4 phase difference layer 21. That is, the brightness increase/decrease rate exceeds 100%, and based on the above simulation, the thickness of the λ/4 phase difference layer 21 is calculated.

Then, the results of the verification experiment are described. In the experiment, the optical layered body 20 shown in FIG. 1 was manufactured in the following manner.

[Formation of linear polarizing layer]

A polarizing film (polarizer layer) having a linear polarization property and a saponified triacetyl cellulose (TAC) film (KC4UYTAC manufactured by Konica Minolta, thickness 40 μm) were bonded together using a nip roller via a water-based adhesive. The bonded product was dried at 60°C for 2 minutes while maintaining a tension of 430 N/m to obtain a linear polarizing layer having a TAC film as a protective film on one side (equivalent to linear polarizing layer 22). The water-based adhesive is prepared by adding 3 parts of carboxyl-modified polyvinyl alcohol (Kuraray Poval KL318, manufactured by Kuraray) and 1.5 parts of water-soluble polyamide epoxy resin (SUMIREZ RESIN650, manufactured by TAOKA CHEMICAL CO., LTD.) to 100 parts of water.

The optical properties of the obtained linear polarizing layer were measured. The measurement was carried out using a spectrophotometer ("V7100", manufactured by JASCO Corporation) with the surface of the polarizing film of the linear polarizing layer obtained as the incident surface. The absorption axis of the polarizing film was the same as the stretching direction of polyvinyl alcohol. The sensitivity-corrected monomer transmittance of the obtained linear polarizing layer was 42.3%, the sensitivity-corrected polarization degree was 99.995%, the monomer color tone a was -0.5, and the monomer color tone b was 3.0.

[Preparation of composition for forming horizontal alignment film]

Mix 5 parts of the photo-alignment material of the following structure (weight average molecular weight: 30,000) and 95 parts of cyclopentanone (solvent). Stir the resulting mixture at 80°C for 1 hour to obtain a composition for forming a horizontal alignment film.

[Preparation of a composition for forming a horizontally aligned liquid crystal cured film]

In order to form a horizontally aligned liquid crystal cured film (A plate), the following polymerizable liquid crystal compound α and polymerizable liquid crystal compound β are used. The polymerizable liquid crystal compound α is produced by the method described in Japanese Patent Publication No. 2010-31223. In addition, the polymerizable liquid crystal compound β is produced by the method described in Japanese Patent Publication No. 2009-173893. The molecular structures are 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 a leveling agent (F-556; manufactured by DIC Corporation) and 6 parts of a polymerization initiator 2-dimethylamino-2-benzyl-1-(4-morpholinylphenyl)butane-1-one (IRGACURE369, manufactured by BASF Japan) were added to 100 parts of the obtained mixture. Furthermore, N-methyl-2-pyrrolidone (NMP) was added to make the solid content concentration 13%, and stirred at 80°C for 1 hour to obtain a composition for forming a λ/4 phase difference layer.

[Formation of λ/4 phase difference layer]

Corona treatment was applied to a cyclic olefin resin (COP) film (ZF-14-50) manufactured by ZEON Corporation of Japan. The corona treatment was performed using TEC-4AX manufactured by USHIO Electric Co., Ltd. The corona treatment was performed once under the conditions of an output of 0.78 kW and a treatment speed of 10 m/min. The COP film fixed on the glass substrate was coated with a composition for forming a horizontal alignment film using a rotary coater and dried at 80°C for 1 minute. The coated film was exposed to polarized UV using a polarized UV irradiation device ("SPOT CURE SP-9", manufactured by USHIO Electric Co., Ltd.) at an axial angle of 45° and a cumulative light amount of 100 mJ/ ^cm2 at a wavelength of 313 nm. The film thickness of the obtained horizontal alignment film was measured with an optical film thickness meter ("F20", manufactured by Film Metrics) and the result was 100nm. In the above coating, the amount of the horizontal alignment film forming composition dripped in and the number of rotations and the rotation mode of the rotor of the rotary coater ("MS-B300", manufactured by MIKASA) were precisely adjusted to obtain a uniform and accurate coating film thickness in the surface.

Next, a λ/4 phase difference layer forming composition was applied to the horizontal alignment film using a spin coater ("MS-B300", manufactured by MIKASA) and dried at 120°C for 1 minute. The coated film was irradiated with ultraviolet light (in a nitrogen environment, a wavelength of 365nm, an accumulated light amount of 500mJ/ ^cm2 ) using a high-pressure mercury lamp ("UNICURE VB-15201BY-A", manufactured by USHIO Electric Co., Ltd.) to form a λ/4 phase difference layer (equivalent to λ/4 phase difference layer 21).

An adhesive layer is laminated on the λ/4 phase difference layer. The film formed by the COP film, the orientation film, and the λ/4 phase difference layer is bonded to the glass through the adhesive layer, and the COP film is peeled off to obtain a sample for measuring the delay.

The retardation at a wavelength of 550nm was measured using a phase difference measuring device ("KOBRA-WPR", manufactured by Oji Instruments Co., Ltd.), and the result was 140.3nm. Furthermore, the thickness of the λ/4 phase difference layer was calculated from the above retardation and refractive index, and the result was 1900nm. In the above coating, the amount of the λ/4 phase difference layer forming composition dripped, the number of rotations of the rotor of the rotary coating machine, the rotation mode of the rotor, the time from coating to drying, and the temperature in the drying furnace were precisely adjusted to obtain the desired and uniform layer thickness and retardation in the surface.

An adhesive layer is laminated on the λ/4 phase difference layer side of the film formed by the above-mentioned COP film, the alignment film and the λ/4 phase difference layer, and the polarizing film side of the linear polarizing layer having a TAC film as a protective film is connected via the above-mentioned adhesive layer to obtain a film formed by the COP film, the alignment film, the λ/4 phase difference layer, the adhesive layer, the polarizing film (polarizer layer), and the TAC film (protective film). Furthermore, the COP film of the film is peeled off, and the adhesive layer is laminated on the alignment film surface of the peeled surface to obtain an optical laminate having an adhesive layer laminated thereon (hereinafter referred to as the "first optical laminate" for convenience of explanation). The portion other than the adhesive layer in the first optical laminate corresponds to the optical laminate 20 of the image display device 1 shown in FIG. 1 .

The transmission spectrum of the first optical multilayer in the wavelength range of 400nm to 500nm was measured to obtain an interference spectrum. It has maximum values at wavelengths of 434nm, 458nm, and 484nm, and minimum values at wavelengths of 446nm and 470nm, confirming that it is the same as the calculation result of Example 1.

An optical multilayer with an adhesive layer was obtained by the same method except that the thickness of the λ/4 phase difference layer was set to 1955nm (hereinafter referred to as the "second optical multilayer" for convenience of explanation). Furthermore, the transmission spectrum of the second optical multilayer in the wavelength range of 400nm to 500nm was measured to obtain an interference spectrum. It has maximum values at wavelengths of 446nm and 470nm, and minimum values at wavelengths of 434nm, 458nm, and 484nm, confirming that it is the same as the calculation result of Comparative Example 1.

In a commercially available smartphone with a built-in organic electroluminescent image display device (hereinafter referred to as "OLED image display device"), the outermost glass and circular polarizer on the viewing side are removed, and the first optical layer is laminated via an adhesive layer on the OLED image display device (equivalent to the image display unit 10) of the smartphone. In this state, the display image of the OLED image display device is displayed in blue, and the brightness of the light output from the first optical layer is confirmed using the display evaluation system DMS803 (manufactured by Instrument Systems GmbH).

The second optical laminate is laminated via an adhesive layer on the OLED image display device (equivalent to the image display unit 10) of the above-mentioned smart phone to replace the first optical laminate, and the brightness of the light output from the second optical laminate is confirmed in the same manner as the first optical laminate. As a result, compared with the smart phone with the OLED image display device laminated with the second optical laminate, the brightness of the peak light emission of the smart phone with the OLED image display device laminated with the first optical laminate is increased by 5%, and the blue light emission can be strongly recognized even with the naked eye.

The present invention is not limited to the above-mentioned embodiments and experimental examples, and includes the scope indicated by the scope of the patent application, and all changes within the meaning and scope that are equivalent to the scope of the patent application.

The image display unit may be an inorganic electroluminescent device having independently luminescent pixels, an electron emission display device (such as a field emission display device (FED), a surface field emission display device (SED)), an electronic paper (a display device using electronic ink or an electrophoretic element), a plasma display device, a projection display device (such as a grating light valve (also known as a GLV) display device), a display device having a digital micromirror device (also known as a DMS), and a piezoelectric ceramic display, etc.

You can also use a bonding agent layer instead of an adhesive layer.

Although the mountain-shaped area M is an area corresponding to any one of the three primary colors, it can also be an area corresponding to other colors (or wavelength ranges).

1: Image display device

2a,2b: Adhesive layer

10: Image display unit

11: Light source

12: Image display layer

20: Optical laminates

21:λ/4 phase difference layer

21a: Page 1

21b: Page 2

22: Linear polarizing layer

111: Luminous Department

211: Phase difference display layer

212: No orientation layer

Claims (10)

An image display device comprises: an image display unit including a light-emitting unit and displaying an image on an image display surface; a λ/4 phase difference layer disposed on the image display surface; and a linear polarization layer disposed on the λ/4 phase difference layer; wherein the light from the light-emitting unit includes a luminescence peak and has a mountain-shaped region with a half-maximum width of less than 60nm; the λ/4 phase difference layer is configured to satisfy condition 1; condition 1: in the interference spectrum of the two surfaces in the thickness direction of the λ/4 phase difference layer, the number of maximum values in the wavelength range defining the half-maximum width is 1 and the number of minimum values is less than 2. An image display device as described in claim 1, wherein the aforementioned λ/4 phase difference layer is further constructed in a manner that satisfies condition 2; condition 2: the difference between the peak wavelength corresponding to the aforementioned luminescence peak and the wavelength corresponding to the aforementioned maximum value of the aforementioned interference spectrum is less than 1/5 of the aforementioned full width at half maximum. An image display device as described in claim 1 or 2, wherein the aforementioned full width at half maximum is 20nm, and the peak wavelength corresponding to the aforementioned luminescence peak is 458±2nm. An image display device as described in claim 1 or 2, wherein the aforementioned full width at half maximum is 40nm, and the peak wavelength corresponding to the aforementioned luminescence peak is 523±2nm. An image display device as described in claim 1 or 2, wherein the aforementioned full width at half maximum is 40nm, and the peak wavelength corresponding to the aforementioned luminescence peak is 530±2nm. An image display device as described in claim 1 or 2, wherein the aforementioned full width at half maximum is 50nm, and the peak wavelength corresponding to the aforementioned luminescence peak is 626±2nm. An image display device as described in claim 1 or 2, wherein the aforementioned λ/4 phase difference layer is a phase difference display layer that imparts a phase difference of λ/4 to light. An image display device as described in claim 1 or 2, wherein the aforementioned λ/4 phase difference layer comprises: a phase difference display layer that imparts a phase difference of λ/4 to light; and a non-aligned layer. An image display device as described in claim 8, wherein the phase difference display layer and the non-aligned layer are closely stacked with each other; the refractive index difference between the phase difference display layer and the non-aligned layer is zero. An image display device as described in claim 1 or 2, wherein the aforementioned λ/4 phase difference layer has a first surface and a second surface opposite to the aforementioned first surface in the aforementioned thickness direction; among the refractive index differences of the plurality of interfaces including the aforementioned first surface and the aforementioned second surface and through which the light output from the aforementioned light-emitting portion passes, the refractive index difference when the aforementioned first surface and the aforementioned second surface are interfaces is greater than the other refractive index differences.

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