Reflective display apparatus

Abstract

A reflective display apparatus is provided with: a reflective device (10); an illumination unit (12) that is disposed on the viewing side of the reflective device (10) and illuminates the reflective device (10) with light; and a block layer (14) that prevents or reduces the transmission of ultraviolet rays or ultraviolet rays and high-energy visible rays in a wavelength region of 380-425 nm. When the reflective device (10) is in white display, BLR<0.5 and BLTF<0.085 are satisfied in either a state in which the illumination unit (12) is turned on or a state in which the illumination unit (12) is not turned on under external light.

Description

reflective display device

[0001] This invention relates to a reflective display device.

[0002] A liquid crystal display device is disclosed (Patent Document 1) comprising: a display panel having a display surface; a light guide plate having an output surface facing the display surface of the display panel and an input surface intersecting the output surface; a light source that incidents light on the input surface; and a light cut layer provided between the light source and the input surface to suppress the transmission of light in a predetermined wavelength range.

[0003] Furthermore, a liquid crystal panel and liquid crystal display device are disclosed that include an absorbing polarizer and a blue light transmission suppression layer disposed on the polarizer to suppress the transmission of blue light in the wavelength range of 380 nm to 500 nm (Patent Document 2).

[0004] Furthermore, a liquid crystal display device is disclosed comprising a liquid crystal display panel and a backlight assembly, wherein a resin layer made of a transparent material, which is a base resin consisting of a photocurable resin that hardens with ultraviolet or visible light, or a transparent epoxy resin, mixed with a predetermined amount of a coloring agent, is provided on the front surface of the liquid crystal display panel (Patent Document 3). The resin layer has been shown to suppress the transmittance of light with a wavelength of 430 nm to 480 nm among the blue light (light with a wavelength of 380 nm to 495 nm) emitted from a white LED, which is a backlight light source, to 40% to 60%.

[0005] Japanese Patent Publication No. 2019-109429, Japanese Patent Publication No. 2016-142942, Japanese Patent Publication No. 2014-202864

[0006] Incidentally, reflective display devices such as reflective liquid crystal displays (LCDs) and electronic paper displays (EPDs) have features such as low power consumption and excellent outdoor visibility in ambient light. On the other hand, reflective display devices require auxiliary lighting to be viewed in dark environments, for example, a front light is used.

[0007] Conventional reflective display devices use white LEDs with a peak around 450 nm as the light source for the front light of the light guide plate system. There are concerns that the light from this light source contains light with wavelengths of 380 nm to 500 nm, known as blue light, which can easily cause eye strain.

[0008] EyeSafe standards have been established to ensure the comfort and safety of observers of display devices. These standards define the Blue Light Ratio (BLR) and Blue Light Toxicity Factor (BLTF), as defined by the following equations (1) and (2). BLTF is a weighted blue light risk ratio relative to display brightness, calculated according to the blue light hazard function (B(λ)). The blue light hazard function can be derived from the values ​​in Table C4 of “Retinal and UVR Hazard Spectral Weighting Functions”, from Threshold Limit Values ​​for Chemical Substances and Physical Agents & Biological Exposure Indices for 2017. Here, L(λ) is the emission spectral value at wavelength λ [μW・cm²]. －２ nm －１ ], Δλ is 1, and g(λ) is the CIE 1931 RGB luminosity function. Furthermore, a scaling factor of 0.001 is used in the wavelength range of 700 nm to 780 nm.

[0009] According to the standards, it is desirable for the BLR to be 0.5 or less and the BLTF to be 0.085 or less.

[0010] However, it was difficult to meet this standard without compromising color accuracy with front lights using a light guide plate system that utilizes a white LED light source. Furthermore, even under ambient light conditions where reflective display devices have excellent visibility, it has not been possible to reduce the amount of reflected blue light contained in ambient light to below the standard without compromising color accuracy (Hertel D.710, Blue-Light Eye Safety Predictions under Ambient Light: ePaper Displays with Front Light vs. Emissive Displays).

[0011] For example, the liquid crystal display device described in Patent Document 1 fails to meet the standard when using sunlight, regardless of whether the front lights are on or off. Furthermore, reflective display devices that utilize sunlight and offer high visibility outdoors, as described in Patent Documents 2 and 3, do not provide the desired effect.

[0012] Furthermore, self-emissive OLED displays such as those in mobile devices have a relatively short product life, and their durability against ambient light is achieved by the UV-cutting performance below 400 nm contained in the TAC of the base material of the anti-reflective circular polarizer. However, applications such as automotive and outdoor use, which are used under ambient light, require even stricter ambient light durability. For this reason, there is a research paper that uses a multilayer refractive index (distributed Bragg reflector) film as an ambient light blocking layer on the observer side of a self-emissive OLED display (Kai-Chen Lin et al., Development of Anti-UV Structure for OLED Display, 1891 SID 2019 DIGEST).

[0013] However, there was a problem in that the performance of the blocking layer was dependent on the angle of incidence of light, and its performance was not sufficient.

[0014] One aspect of the present invention comprises a reflective device, an illumination unit disposed on the viewing side of the reflective device and irradiating the reflective device with light, and a blocking layer that prevents or reduces the transmission of ultraviolet light or ultraviolet light and high-energy visible light in the wavelength range of 380 nm to 425 nm, characterized in that when the reflective device is displayed in white, BLR ≤ 0.5 and BLTF ≤ 0.085 are satisfied in either the state when the illumination unit is lit or when the illumination unit is not lit under ambient light.

[0015] In this case, it is preferable that the block layer is positioned on the side of the illumination unit that is visible to the naked eye.

[0016] Furthermore, the illumination unit preferably comprises a light guide plate having an output surface facing the display surface of the reflective device and an input surface intersecting the output surface, and a light source that incidents light onto the input surface.

[0017] Furthermore, the illumination unit preferably includes an organic electroluminescent element comprising a first transparent substrate, an anode, an organic layer, a cathode arranged to form a periodic pattern, and a second transparent substrate facing the first transparent substrate, with respect to the viewing side.

[0018] Furthermore, the emission spectrum of the illumination unit preferably has a ratio of peak intensity around 450 nm to peak intensity around 475 nm within the range of 1.1 to 1.45, and a color temperature of 5600 K or less.

[0019] Furthermore, it is preferable that the light transmittance of the block layer in the 380 nm to 405 nm range is 5% or less, and the maximum value of the light transmittance in the range from 405 nm to 425 nm is 90% or less.

[0020] Furthermore, it is preferable that the light transmittance of the block layer at 380 nm or less is 5% or less.

[0021] Furthermore, the block layer is an adhesive layer comprising an acrylic copolymer, a first ultraviolet absorber, and a second ultraviolet absorber, wherein the first ultraviolet absorber is a 2-phenylbenzotriazole derivative having a thioaryl ring group, the second ultraviolet absorber is liquid at room temperature, and the content of the second ultraviolet absorber is preferably 1 to 10 times the content of the first ultraviolet absorber.

[0022] Furthermore, the second ultraviolet absorber is preferably a benzotriazole derivative.

[0023] Furthermore, it is preferable that the lighting unit has a touch panel on the viewing side, and that the block layer is arranged on either the viewing side of the touch panel or the lighting unit side.

[0024] Furthermore, the reflective device is preferably a reflective electronic paper display.

[0025] Furthermore, the reflective device is preferably a reflective liquid crystal display.

[0026] According to the present invention, it is possible to provide a reflective display device that emits blue light below a standard level without impairing color reproduction, both outdoors and indoors.

[0027] This is a schematic cross-sectional diagram showing an example of the configuration of a reflective display device in an embodiment of the present invention. diagram showing the spectral characteristics of a direct-type OLED used in the example. This is a diagram showing the wavelength dependence of the transmittance of the optical adhesive layer used as a block layer in an embodiment of the present invention. This is a diagram showing the radiance measurement status in the example and comparative example. This is a diagram showing a table of evaluation results for the example and comparative example of the present invention. This is a diagram showing the wavelength dependence of Comparative Example 1-1 in Comparative Example 1 in the wavelength range of 380 nm to 780 nm, and the wavelength dependence of Comparative Example 1-1 in the same wavelength range, using the blue light hazard function. This is a diagram showing the wavelength dependence of Comparative Example 1-1 in Comparative Example 1, Comparative Example 2-1 in Comparative Example 2, and Example 1-1 in Example 1 in the wavelength range of 380 nm to 500 nm, using the normalized intensity. This figure shows the wavelength dependence of normalized intensity for Comparative Example 1-1 in Comparative Example 1, Comparative Example 2-1 in Comparative Example 2, and Example 1-1 in Example 1 in the wavelength range of 380 nm to 440 nm. This figure shows the wavelength dependence of normalized intensity for Comparative Example 1-2 in Comparative Example 1, Comparative Example 2-2 in Comparative Example 2, and Example 1-2 in Example 1 in the wavelength range of 380 nm to 500 nm. This figure shows the wavelength dependence of normalized intensity for Comparative Example 5-1 in Comparative Example 5 in the wavelength range of 380 nm to 780 nm, and the wavelength dependence of Comparative Example 5-1 in the same wavelength range using the blue light hazard function. This figure shows the wavelength dependence of normalized intensity for Comparative Example 5-1 in Comparative Example 5, Comparative Example 6-1 in Comparative Example 6, and Example 3-1 in Example 3 in the wavelength range of 380 nm to 500 nm.

[0028] A reflective display device 100 according to an embodiment of the present invention comprises, for example, as shown in FIG. 1, a reflective device 10, an illumination unit 12, a blocking layer 14, a touch panel 16, and a low-reflection layer 18.

[0029] The reflective device 10 is a component having a display function in the reflective display device 100. The reflective device 10 may be, for example, a reflective electronic paper display or a reflective liquid crystal display.

[0030] The illumination unit 12 is a component called a front light that has a light irradiation function for the reflective device 10. The illumination unit 12 is disposed on the visible side of the reflective device 10 (the side on which a user views a display) in the reflective display device 100.

[0031] The illumination unit 12 may be configured to include, for example, a light guide plate having an emission surface facing the display surface of the reflective device 10 and an incident surface intersecting the emission surface. Further, the illumination unit 12 may be configured to include an organic electroluminescence element including, toward the visible side of the reflective display device 100, a first transparent substrate, an anode, an organic layer, a cathode arranged with a periodic pattern formed thereon, and a second transparent substrate facing the first transparent substrate.

[0032] When the illumination unit 12 is configured to include an organic electroluminescence element, it is preferable that the illumination unit 12 exhibits an emission spectrum having two peaks near 450 nm and near 475 nm. Here, the term "near 450 nm" means a wavelength range of 440 nm to 460 nm. Further, the term "near 475 nm" means a wavelength range of 465 nm to 485 nm. It is preferable that the illumination unit 12 adjusts the ratio of the peak intensity near 450 nm to the peak intensity near 475 nm to 1.1 to 1.45, and changes the material ratio of the green region near 520 nm (510 nm to 530 nm) and the red region near 613 nm (603 nm to 623 nm), thereby providing a light source having a color tone with a color temperature of 5600 K or lower. From the viewpoint of preventing the display screen from becoming reddish when used as an illumination unit for a reflective device, the color temperature is more preferably more than 4000 K and 5600 K or lower.

[0033] The blocking layer 14 is a layer that prevents or reduces the transmission of light in the ultraviolet region and some light in the visible region. The blocking layer 14 is located on the viewing side of the illumination unit 12 or on the reflective device 10 side. The blocking layer 14 may be located on either the viewing side or the opposite side of the touch panel 16, which will be described later. Furthermore, if the outermost surface of the reflective display device 100 is covered with a low-reflection layer 18 or cover glass, it is preferable to place the blocking layer 14 beneath it. The thickness of the blocking layer is not particularly limited, but from the viewpoint of maintaining optical properties, it is preferable to have a thickness of 25 μm to 100 μm.

[0034] The blocking layer 14 prevents or reduces the transmission of ultraviolet light in the 380 nm to 425 nm range, or ultraviolet light and high-energy visible light. Furthermore, it is preferable that the blocking layer 14 prevents or reduces the transmission of light in the wavelength range of ultraviolet light and high-energy visible light below 425 nm. Specifically, it is preferable that the blocking layer 14 has a light transmittance of 5% or less in the 380 nm to 405 nm range, and a maximum light transmittance of 90% or less in the range between 405 nm and 425 nm. It is also preferable that the blocking layer 14 has a light transmittance of 5% or less below 380 nm.

[0035] The block layer 14 can be an adhesive layer containing an acrylic copolymer, a first ultraviolet absorber, and a second ultraviolet absorber. The first ultraviolet absorber is preferably a 2-phenylbenzotriazole derivative having a thioaryl ring group. The second ultraviolet absorber is preferably a liquid at room temperature. For example, the second ultraviolet absorber is preferably a benzotriazole derivative. The content of the second ultraviolet absorber is preferably 1 to 10 times the content of the first ultraviolet absorber.

[0036] The touch panel 16 is a component having a function of detecting a position touched by a user or a position approached by a user in the reflective display device 100. The touch panel 16 may be, for example, a capacitive touch panel. A capacitive touch panel includes a plurality of first electrodes extending in the X direction and arranged side by side along the Y direction intersecting the X direction, and a plurality of second electrodes extending in the Y direction and arranged side by side along the X direction, which are stacked with an insulating layer interposed therebetween. The first electrodes and the second electrodes are made of a transparent conductive material that transmits the wavelength of light emitted from the reflective device 10 and the illumination unit 12. It is preferable that the first electrodes and the second electrodes are made of a transparent conductive material such as indium tin oxide (ITO: Indium Tin Oxide) or indium zinc oxide (IZO: Indium Zinc Oxide), for example. In such a configuration, by detecting the position in the Y direction of the first electrode where the capacitance has changed and the position in the X direction of the second electrode where the capacitance has changed, it is possible to detect the position touched by the user or the position approached by the user.

[0037] In the reflective display device 100 described above, the touch panel 16 is provided on the viewing side of the block layer 14; however, as shown in FIG. 2, a configuration may be adopted such as that of a reflective display device 102 in which the touch panel 16 is provided on the opposite side of the block layer 14 from the viewing side.

[0038] Furthermore, as shown in FIG. 3, a configuration may be adopted such as that of a reflective display device 104 in which the touch panel 16 is not provided. Further, as shown in FIG. 4, a configuration may be adopted such as that of a reflective display device 106 in which a block layer 14 is provided on the reflective device 10 side of the illumination unit 12. Note that even in configurations provided with the touch panel 16 like the reflective display devices 100 and 102, a configuration in which the block layer 14 is provided on the reflective device 10 side of the illumination unit 12 may also be adopted.

[0039] The low-reflection layer 18 is a component having an anti-reflective function to reduce the reflection of ambient light incident from the viewing side of the reflective display device 100. The low-reflection layer 18 is a thin coating layer applied to the viewing surface of the reflective display device 100. By providing the low-reflection layer 18, glare and reflections can be reduced even outdoors or under bright lighting. The low-reflection layer 18 uses a material with a controlled refractive index to suppress light reflection. For example, the low-reflection layer 18 is made of silicon oxide (SiO ２ ), titanium oxide (TiO ２ ) and others are used.

[0040] The low-reflection layer 18 may be provided as needed, and a configuration without the low-reflection layer 18 is also possible. In addition, depending on the application, a transparent layer such as a cover glass may be provided instead of the low-reflection layer 18.

[0041] In the reflective display devices 100, 102, 104, and 106 of this embodiment, when the reflective device 10 is set to display white, in either the state when the illumination unit 12 is lit or when the illumination unit 12 using ambient light is not lit, the BLR shown in formula (1) above is 0.5 or less and the BLTF shown in formula (2) above is 0.085 or less.

[0042] By satisfying these conditions, the reflected light from the illumination unit 12 to the reflective device 10, and the leaked light to the observer side when the illumination unit 12 uses a light guide plate, can be attenuated to a safe level by reducing the amount of blue light in the wavelength range. Furthermore, when there is ambient light such as sunlight and the illumination unit 12 is not used, the reflective display device 100 can be used at a safe level while maintaining visibility by attenuating the blue light contained in the ambient light or sunlight and then observing the reflected light.

[0043] Furthermore, since the blocking layer 14 attenuates ultraviolet rays and high-energy visible light, the durability of a reflective display device including an organic electroluminescent element can be increased.

[0044] Furthermore, ΔE, an indicator of color change, is measured using a spectroradiometer with L as the reference value for a standard white plate. * a *and b * is obtained from measured values. ΔE is an index that numerically represents color difference, and is mainly used to evaluate changes in hue and color consistency. By quantitatively expressing color difference, it indicates how visually different two colors appear. In the present invention, ΔE is evaluated according to the following criteria: ΔE ≤ 2: no color difference perceived; 2 < ΔE ≤ 7: a slight color difference is perceived but does not cause concern; 7 < ΔE: a color difference is perceived. That is, when ΔE is 7 or less, it is evaluated that the color difference between the two reflective display devices does not cause concern and has no visual problem.

[0045] ΔE, which is an index of hue change, is obtained from measurement of two target samples to obtain respective L ＊ a ＊ b ＊ values in the color space according to the following mathematical formula (3). (Math 3) ΔE=√(L1 * -L2 * )^2+(a1 * -a2 * )^2+(b1 * -b2 * )^2) ・・・(3)

[0046] In addition, YI (Yellow Index), which is an index of yellowing, is obtained for the tristimulus values XYZ measured by a spectroradiometer in an outdoor light simulation state using the daylight source D65, according to the following mathematical formula (4) defined in JIS K7373. It is known that the smaller the value, the lower the yellowing. In the present invention, YI is evaluated according to the following criteria: 7 < YI ≤ 30: low yellowing; 5 < YI ≤ 7: very low yellowing; YI ≤ 5: extremely low yellowing. That is, when YI is 30 or less, it is evaluated that the yellowing of the reflective display device has no visual problem. (Math 4) YI=100(1.2985X-1.1335Z) / Y ・・・(4)

[0047] [Examples and Comparative Examples] First, in the examples and comparative examples of the present invention, each example and comparative example was evaluated under two conditions: "when the illumination unit is lit" and "when the illumination unit is not lit under ambient light," with the reflective device displayed in white. To make this clearer, from now on, when the reflective device is displayed in white and the illumination unit is lit, the names of each example and comparative example will be given with "-1" added to the end, and when the reflective device is displayed in white and the illumination unit is not lit, the names of each example and comparative example will be given with "-2" added to the end. For example, "Example 2" and "Comparative Example 3" will be referred to as "Comparative Example 2-1" and "Comparative Example 3-1" respectively when the reflective device is displayed in white and the illumination unit is lit, and as "Comparative Example 2-2" and "Comparative Example 3-2" respectively when the reflective device is displayed in white and the illumination unit is lit.

[0048] Furthermore, in the examples and comparative examples, the evaluation was performed using the configuration of the reflective display device 104 shown in Figure 3. However, in Comparative Examples 1, 3, and 5, a block layer was not used in the configuration.

[0049] In Examples 1 and 2 and Comparative Examples 1 to 4, the reflective device was an EPD (Electronic Panel Detector). Specifically, the EPD was an Amazon Kindle Paperwhite 6th generation. In Examples 3 and Comparative Examples 5 and 6, the reflective device was a color reflective liquid crystal (LCD). The color reflective LCD used was a PIC3201 manufactured by Pictleep.

[0050] In Example 1 and Comparative Examples 1 and 2, the illumination unit, which is the front light, was a light guide plate system comprising a light guide plate having an output surface facing the display surface of the reflective device and an input surface intersecting the output surface, and a white LED light source that incident light on the input surface.

[0051] Regarding the "external light" mentioned above, in this embodiment and comparative example, the use of external light was simulated. In this case, as shown in Figure 7, a rod-shaped D65 light source was used as the illumination device 202 and positioned so as to be incident on the display surface of the reflective display device 104 at a 30-degree angle. A shielding curtain 204 was placed behind it, and measurements were taken without turning on the illumination section of the reflective display device 104.

[0052] In Examples 2 and 3 and Comparative Examples 3 to 6, the illumination unit, which served as the front light, was a direct-type OLED. The direct-type OLED used had two peaks in its emission spectrum, one around 450 nm (440 nm to 460 nm) and the other around 475 nm (465 nm to 485 nm). Furthermore, by adjusting the ratio of the peak intensity around 450 nm to the peak intensity around 475 nm within the range of 1.1 to 1.45, and by changing the material ratio between the green region around 520 nm (510 nm to 530 nm) and the red region around 613 nm (603 nm to 623 nm), illumination units with color temperatures of 5600 K and 4000 K were fabricated.

[0053] Figure 5 shows the emission spectra of a light source with a color temperature of 5600K (solid line in the figure) and a light source with a color temperature of 4000K (dashed line in the figure). When the peak intensity around 450 nm (hereinafter referred to as the normalized intensity) is 1 and the normalized intensity around 475 nm is 0.839, the ratio of the peak intensities is 1 / 0.839 = 1.19, and the color temperature at that time was 5600K. Also, when the normalized intensity around 450 nm is 0.648 and the normalized intensity around 475 nm is 0.462, the ratio of the peak intensities is 0.648 / 0.0462 = 1.4, and the color temperature at that time was 4000K.

[0054] From the perspective of blue light safety standards, a lighting unit with a lower color temperature of 4000K emits less blue light, resulting in a BLTF lower than the standard. However, using a low color temperature light source as the lighting unit for a reflective device is undesirable because it causes the display screen to appear reddish. In the examples and comparative examples of the present invention, comparative examples 3 and 5 were applied to lighting units with a color temperature of 4000K, while examples 2 and 3 and comparative examples 4 and 6 were applied to lighting units with a color temperature of 5600K, which can achieve white reflected light close to daylight.

[0055] The low-reflection layer used was XR60 manufactured by Toppan Tomoegawa Optical Film Co., Ltd. The low-reflection layer was bonded to the visible side of the illuminated part, which is the front light. In this embodiment, the low-reflection layer was bonded to the visible side of the illuminated part via a block layer (described later).

[0056] The block layer used an optical adhesive layer. Specifically, the block layers of Examples 1 to 3 used "Adhesive 1" with a thickness of 100 μm, which is an ultraviolet and high-energy visible light absorbing type as described in Example 1 of International Publication No. WO2022 / 209476.

[0057] Furthermore, the block layers of Comparative Examples 2, 4, and 6 similarly used a 100 μm thick "adhesive a" of the UV-absorbing type, which is made from a coating containing one type of powdered UV absorber, as described in Comparative Example 1 of International Publication No. WO2022 / 209476.

[0058] Furthermore, in Comparative Examples 1, 3, and 5, TD06A, an acrylic adhesive with a thickness of 25 μm manufactured by Tomoegawa Paper Co., Ltd., was used as the "transparent adhesive."

[0059] Adhesive a comprises an acrylic copolymer and a first ultraviolet absorber. Adhesive 1 also comprises an acrylic copolymer, a first ultraviolet absorber, and a second ultraviolet absorber. The first ultraviolet absorber is a 2-phenylbenzotriazole derivative having a thioaryl ring group. The second ultraviolet absorber is a benzotriazole derivative that is liquid at room temperature. The content of the second ultraviolet absorber is five times that of the first ultraviolet absorber.

[0060] Figure 6 shows the wavelength dependence of the transmittance of adhesive a, which is an ultraviolet-absorbing type, and adhesive 1, which is an ultraviolet and high-energy visible light-absorbing type. Although not shown in the figure, adhesive a, which is an ultraviolet-absorbing type, exhibits a transmittance characteristic of 5% or less in the light transmittance below 380 nm. On the other hand, adhesive 1, which is an ultraviolet and high-energy visible light-absorbing type, exhibits a transmittance characteristic of 5% or less in the light transmittance below 380 nm, 5% or less in the light transmittance between 380 nm and 405 nm, and a maximum light transmittance of 0.990% or less in the light transmittance between 405 nm and 425 nm.

[0061] Figure 7 shows the radiance measurement conditions for which normalized intensity is derived in the embodiments and comparative examples of the present invention. For the measurements, a Topcon Techno House SR-UL1R spectroradiometer was used as the measuring instrument 200. When the illumination section of the reflective display device 104 was in use, the measuring instrument 200 was placed on the normal to the display surface of the reflective display device 104 in a darkroom for the measurement. The distance between the surface of the reflective display device 104 and the measuring instrument 200 was 1 m. In the ambient light simulation state (with the illumination section of the reflective display device 104 not lit), a rod-shaped D65 daylight light source was used as the illumination device 202. The illumination device 202 was positioned so as to be incident on the display surface of the reflective display device 104 at a 30-degree angle, and a shielding curtain 204 was placed behind it for the measurement without illuminating the illumination section of the reflective display device 104. The measurement conditions were to measure the radiance from 380 nm to 780 nm at a measurement angle of 1 degree for every 1 nm.

[0062] Furthermore, by performing correction using a standard white plate with this measuring instrument, L * a * and b * The following measurements were taken. Furthermore, the values ​​of BLR and BLTF were obtained by calculating them using formulas (1) and (2) from the values ​​obtained from SR-UL1R.

[0063] Furthermore, regarding the illumination section of the reflective display device, when a color reflective liquid crystal is used as the reflective device, a light guide plate system where the angle of incidence of light to the reflective device is not in the normal direction results in a decrease in contrast due to light leakage caused by reflected light, which makes it impractical. Therefore, in this invention, evaluation of the combination of color reflective liquid crystal and the light guide plate system was not performed.

[0064] Figure 8 shows a summary table of evaluation results for Examples 1-3 and Comparative Examples 1-6.

[0065] Figure 9 shows the wavelength dependence of Comparative Example 1-1 by normalized intensity in the wavelength range of 380 nm to 780 nm (solid line in the figure) and the wavelength dependence of Comparative Example 1-1 by the blue light hazard function in the same wavelength range (dashed line in the figure).

[0066] Figure 10 shows graphs of the wavelength dependence of normalized intensity for Comparative Example 1-1 (dashed line in the figure) in Comparative Example 1, Comparative Example 2-1 (dotted line in the figure) in Comparative Example 2, and Example 1-1 (solid line in the figure) in Example 1, in the wavelength range of 380 nm to 500 nm, which greatly affects the values ​​of BLR and BLTF.

[0067] Furthermore, Figure 11 shows graphs of the wavelength dependence of normalized intensity for Comparative Example 1-1 (dashed line in the figure) in Comparative Example 1, Comparative Example 2-1 (dotted line in the figure) in Comparative Example 2, and Example 1-1 (solid line in the figure) in Example 1, in the wavelength range of 380 nm to 440 nm.

[0068] As shown in the table in Figure 8, Comparative Example 2-1 in Comparative Example 2 uses an EPD as the reflective device, applies an ultraviolet-absorbing adhesive a to the block layer, and uses a light guide plate system as the illumination part, but the BLR was 0.53 and the BLTF was 0.080. In other words, the BLR failed to meet the standard of 0.5 or less.

[0069] In contrast, Example 1-1 in Example 1 uses an EPD as the reflective device, applies an adhesive 1 which is of the ultraviolet-absorbing and high-energy visible light-absorbing type to the block layer, and uses a light guide plate method as the illumination part, resulting in a BLR of 0.46 and a BLTF of 0.077. That is, it was possible to satisfy the standard BLR of 0.5 or less and the standard BLTF of 0.085 or less.

[0070] In Comparative Example 1-1, a reflective device was used as an EPD, without a block layer, and a light guide plate system was used as the illumination section. However, the BLR was 0.54 and the BLTF was 0.086. In other words, neither the BLR (which is 0.5 or less) nor the BLTF (which is 0.085 or less) met the standard.

[0071] Figure 12 shows graphs of the wavelength dependence of normalized intensity for Comparative Example 1-2 in Comparative Example 1 (dashed line in the figure), Comparative Example 2-2 in Comparative Example 2 (dotted line in the figure), and Example 1-2 in Example 1 (solid line in the figure) in the wavelength range of 380 nm to 500 nm, which greatly affects the values ​​of BLR and BLTF.

[0072] As shown in the table in Figure 8, Comparative Example 2-2 in Comparative Example 2 uses an EPD as the reflective device, applies an ultraviolet-absorbing adhesive a to the block layer, and uses a light guide plate system as the illumination part, but without lighting it. The evaluation was performed under ambient light simulation conditions using a rod-shaped D65 light source as the illumination device, and the BLR was 0.42 and BLTF was 0.091. In other words, the BLTF failed to meet the standard of 0.085 or less.

[0073] In contrast, Example 1-2 in Example 1 uses an EPD as the reflective device, applies adhesive 1 which is of the ultraviolet absorbing and high-energy visible light absorbing layer type to the block layer, and uses a light guide plate method as the illumination part, but without lighting it. The evaluation was performed in an ambient light simulation state using a rod-shaped D65 light source as the illumination device, and the BLR was 0.42 and BLTF was 0.077. In other words, the BLR was able to satisfy the standard of 0.5 or less and the BLTF was able to satisfy the standard of 0.085 or less.

[0074] In Comparative Example 1, Comparative Example 1-2 used an EPD (Electromagnetic Distribution Panel) as the reflective device, without a block layer, and employed a light guide plate system as the illumination unit, but without illumination. The evaluation was performed under ambient light simulation conditions using a rod-shaped D65 light source as the illumination device, resulting in a BLR of 0.42 and a BLTF of 0.090. In other words, the condition of a BLTF of 0.085 or less, which is the standard, could not be met.

[0075] As shown in the table in Figure 8, Comparative Example 4-1 in Comparative Example 4 uses an EPD as the reflective device, applies an ultraviolet-absorbing adhesive a to the block layer, and uses a direct-type OLED with a color temperature of 5600K as the illumination part, resulting in a BLR of 0.41 and a BLTF of 0.074. In other words, it was possible to satisfy the standard BLR of 0.5 or less and the standard BLTF of 0.085 or less.

[0076] However, in Comparative Example 4-2, which was evaluated under ambient light simulation conditions with the direct-type OLED not lit and a rod-shaped D65 light source used as the illumination device, the BLR was 0.42 and the BLTF was 0.089. In other words, the BLTF failed to meet the standard of 0.085 or less.

[0077] In contrast, Example 2-1 in Example 2 uses an EPD as the reflective device, applies an adhesive 1 which is of the ultraviolet-absorbing and high-energy visible light-absorbing type to the block layer, and uses a direct-type OLED with a color temperature of 5600K as the illumination part, but the BLR was 0.42 and the BLTF was 0.074. In other words, it was possible to satisfy the standard BLR of 0.5 or less and the standard BLTF of 0.085 or less.

[0078] Furthermore, in Example 2-2, which is an evaluation under ambient light simulation conditions where the direct-type OLED is not lit and a rod-shaped D65 light source is used as the illumination device, the BLR was 0.42 and the BLTF was 0.076. In other words, the BLR was able to satisfy the standard of 0.5 or less and the BLTF was able to satisfy the standard of 0.085 or less.

[0079] In Comparative Example 3-1, used an EPD as the reflective device, without a blocking layer, and employed a direct-type OLED with a color temperature of 4000K as the illumination unit. The BLR was 0.42 and the BLTF was 0.075. In other words, the BLR was able to meet the standard of 0.5 or less, and the BLTF was able to meet the standard of 0.085 or less.

[0080] However, in Comparative Example 3-2, which was evaluated under ambient light simulation conditions with the direct-type OLED not lit and a rod-shaped D65 light source used as the illumination device, the BLR was 0.42 and the BLTF was 0.091. In other words, the BLTF failed to meet the standard of 0.085 or less.

[0081] As described above, in the configuration in which EPD is applied as a reflective device and adhesive 1, which is of the ultraviolet-absorbing and high-energy visible light-absorbing type, is applied to the block layer, both Example 1 and Example 2 were able to satisfy the standard BLR of 0.5 or less and the standard BLTF of 0.085 or less.

[0082] Next, Example 3 and Comparative Examples 5 and 6 will be described. In these examples, a color reflective liquid crystal was used as the reflective device.

[0083] Figure 13 shows the wavelength dependence of Comparative Example 5-1 by normalized intensity in the wavelength range of 380 nm to 780 nm (solid line in the figure) and the wavelength dependence of Comparative Example 5-1 by blue light hazard function in the same wavelength range (dashed line in the figure).

[0084] Figure 14 shows graphs of the wavelength dependence of normalized intensity for Comparative Example 5-1 (dashed line in the figure) in Comparative Example 5, Comparative Example 6-1 (dotted line in the figure) in Comparative Example 6, and Example 3-1 (solid line in the figure) in Example 3, in the wavelength range of 380 nm to 500 nm, which greatly affects the values ​​of BLR and BLTF.

[0085] As shown in the table in Figure 8, Comparative Example 6-1 in Comparative Example 6 uses a color reflective liquid crystal as the reflective device, applies an ultraviolet-absorbing adhesive a to the block layer, and uses a direct-type OLED with a color temperature of 5600K as the illumination part, but the BLR was 0.28 and the BLTF was 0.081. In other words, it was possible to satisfy the standard BLR of 0.5 or less and the standard BLTF of 0.085 or less.

[0086] However, in Comparative Example 6-2, which was evaluated under ambient light simulation conditions with the direct-type OLED not lit and a rod-shaped D65 light source used as the illumination device, the BLR was 0.36 and the BLTF was 0.088. In other words, the BLTF failed to meet the standard of 0.085 or less.

[0087] In contrast, Example 3-1 in Example 3 uses a color reflective liquid crystal as the reflective device, applies an adhesive 1 that absorbs ultraviolet light and high-energy visible light to the block layer, and uses a direct-type OLED with a color temperature of 5600K as the illumination part, resulting in a BLR of 0.29 and a BLTF of 0.081. That is, it was possible to satisfy the standard BLR of 0.5 or less and the standard BLTF of 0.085 or less.

[0088] Furthermore, in Example 3-2, which is an evaluation under ambient light simulation conditions where the direct-type OLED is not lit and a rod-shaped D65 light source is used as the illumination device, the BLR was 0.36 and the BLTF was 0.083. In other words, the BLR was able to satisfy the standard of 0.5 or less and the BLTF was able to satisfy the standard of 0.085 or less.

[0089] In Comparative Example 5-1, used a color reflective liquid crystal as the reflective device, without a block layer, and a direct-type OLED with a color temperature of 4000K as the illumination unit. The BLR was 0.29 and the BLTF was 0.083. In other words, the BLR was able to meet the standard of 0.5 or less and the BLTF was able to meet the standard of 0.085 or less.

[0090] However, in Comparative Example 5-2, which was evaluated under ambient light simulation conditions with the direct-type OLED not lit and a rod-shaped D65 light source used as the illumination device, the BLR was 0.36 and the BLTF was 0.088. In other words, the BLTF failed to meet the standard of 0.085 or less.

[0091] As described above, in Example 3, in which a color reflective liquid crystal is applied as the reflective device and adhesive 1, which is of the ultraviolet absorbing and high-energy visible light absorbing type, is applied to the block layer, it was possible to satisfy the standard BLR of 0.5 or less and the standard BLTF of 0.085 or less.

[0092] Furthermore, for Examples 1 to 3 and Comparative Examples 1 to 6, ΔE, which is an indicator of color change, was obtained by measurement using the above-mentioned spectroradiometer SR-UL1R. *a * and b * The result was calculated using formula (3). The result is as follows. (Related to Example 1) Example 1-1 in Example 1 and Comparative Example 1-1 in Comparative Example 1: ΔE value "2.5" Example 1-1 in Example 1 and Comparative Example 2-1 in Comparative Example 2: ΔE value "0.6" Example 1-2 in Example 1 and Comparative Example 1-2 in Comparative Example 1: ΔE value "6.0" Example 1-2 in Example 1 and Comparative Example 2-2 in Comparative Example 2: ΔE value "4.1" (Related to Example 2) Example 2-1 in Example 2 and Comparative Example 3-1 in Comparative Example 3: ΔE value "3.1" Example 2-1 in Example 2 and Comparative Example 4-1 in Comparative Example 4: ΔE value "3.1" Example 2-2 in Example 2 and Comparative Example 3-2 in Comparative Example 3: ΔE value "3.4" Example 2-2 in Example 2 and Comparative Example 4-2 in Comparative Example 4: ΔE value "2.4" (Related to Example 3) Example 3-1 in Example 3 and Comparative Example 5-1 in Comparative Example 5: ΔE value "1.4" Example 3-1 in Example 3 and Comparative Example 6-1 in Comparative Example 6: ΔE value "0.9" Example 3-2 in Example 3 and Comparative Example 5-2 in Comparative Example 5: ΔE value "4.0" Example 3-2 in Example 3 and Comparative Example 6-2 in Comparative Example 6: ΔE value "4.0"

[0093] Furthermore, the two samples used in each of the ΔE value calculations described above were visually inspected, and no noticeable color difference was observed in any of them. Based on these visual inspection results and the ΔE evaluation criteria of the present invention, it was found that the reflective display devices of Examples 1 to 3 have no visually problematic issues with respect to color difference.

[0094] Furthermore, for Examples 1 to 3, the yellowness index YI was calculated using formula (4) from the tristimulus values ​​XYZ obtained by the spectroradiometer SR-UL1R under the above ambient light simulation conditions. The results were as follows: Example 1, Example 1-2: YI value "21.6" Example 2, Example 2-2: YI value "5.8" Example 3, Example 3-2: YI value "-2.2"

[0095] Furthermore, each sample used in the calculation of the YI values ​​described above was visually inspected, and no yellowing was noticeable in any of them. Based on these visual results and the YI evaluation criteria of the present invention, it was found that the reflective display devices of Examples 1 to 3 have no visual problems regarding yellowing, and in particular, Example 3-2 in Example 3 had extremely little yellowing numerically.

[0096] In summary, when either an EPD or a color reflective liquid crystal was used as the reflective device, an adhesive 1 that absorbs ultraviolet light and high-energy visible light was applied to the block layer, and either a light guide plate system or a direct-type OLED with a color temperature of 5600K was used as the illumination unit, both the BLR and BLTF standards were met. Furthermore, even when the illumination unit of the reflective display unit was turned off and a rod-shaped D65 light source was used as the illumination device in an ambient light simulation, both the BLR and BLTF standards were met. In other words, it was found that a reflective display unit can be provided in which blue light levels remain below the standard under both outdoor and indoor conditions.

[0097] In addition, it was found that the reflective display devices of Examples 1 to 3 have no visual problems with color difference and yellowing, and can provide reflective display devices that do not impair color.

[0098] Here, when a direct-type OLED is used as the illumination unit, by adjusting the ratio of the peak intensity around 450 nm to the peak intensity around 475 nm within the range of 1.1 to 1.45, and by changing the material ratio of the green region around 520 nm to the red region around 613 nm, the color temperature can be set to less than 5600 K (e.g., 4000 K), even if the block layer is transparent adhesive or adhesive a when lit, the blue light can be kept below the standard value (Comparative Examples 3-1 and 5-1). However, in order to keep the blue light below the standard value when used under ambient light, it is necessary to provide a block layer that absorbs ultraviolet light and high-energy visible light.

[0099] Furthermore, in the reflective display device configurations of Examples 2 and 3, in which the block layer is provided on the viewing side of the illumination unit, degradation of the organic layer of the direct-type OLED, which is the illumination unit, due to irradiation with short-wavelength light can be suppressed, and the luminous efficiency can be maintained over a long period of time. In other words, when a direct-type OLED is used as the illumination unit, by using an ultraviolet-absorbing and high-energy visible light-absorbing type as the block layer on the viewing side (observer side), degradation of the organic layer of the illumination unit can be suppressed, and a decrease in luminous efficiency can be prevented.

[0100] In this example, the configuration of the reflective display device 104 was evaluated, but similar characteristics can be obtained with the configurations of the reflective display devices 100, 102, and 106.

[0101] Based on the above, the present invention has made it possible to provide a reflective display device that emits blue light below the standard level without impairing color reproduction, both outdoors and indoors.

[0102] [Configuration of the present invention] [Configuration 1] A reflective display device comprising: a reflective device; an illumination unit disposed on the viewing side of the reflective device and irradiating the reflective device with light; and a blocking layer that prevents or reduces the transmission of ultraviolet light or ultraviolet light and high-energy visible light in the wavelength range of 380 nm to 425 nm, wherein when the reflective device is set to display white, BLR ≤ 0.5 and BLTF ≤ 0.085 are satisfied in either the state when the illumination unit is lit or when the illumination unit is not lit under ambient light. [Configuration 2] A reflective display device according to Configuration 1, wherein the blocking layer is disposed on the viewing side of the illumination unit. [Configuration 3] A reflective display device according to Configuration 1 or 2, wherein the illumination unit comprises: a light guide plate having an emitting surface facing the display surface of the reflective device and an incident surface intersecting the emitting surface; and a light source that incidents light on the incident surface. [Configuration 4] A reflective display device according to Configuration 1 or 2, wherein the illumination unit includes an organic electroluminescent element comprising a first transparent substrate, an anode, an organic layer, a cathode arranged to form a periodic pattern, and a second transparent substrate facing the first transparent substrate, facing the viewing side. [Configuration 5] A reflective display device according to Configuration 4, wherein the emission spectrum of the illumination unit is characterized in that the ratio of the peak intensity around 450 nm to the peak intensity around 475 nm is in the range of 1.1 to 1.45, and the color temperature is 5600 K or less. [Configuration 6] A reflective display device according to any one of Configurations 1 to 5, wherein the light transmittance of the block layer at 380 nm to 405 nm is 5% or less, and the maximum value of the light transmittance between 405 nm and 425 nm is 90% or less. [Configuration 7] A reflective display device according to any one of Configurations 1 to 6, wherein the light transmittance of the block layer at 380 nm or less is 5% or less.[Configuration 8] A reflective display device according to Configuration 6 or 7, wherein the block layer is an adhesive layer comprising an acrylic copolymer, a first ultraviolet absorber, and a second ultraviolet absorber, wherein the first ultraviolet absorber is a 2-phenylbenzotriazole derivative having a thioaryl ring group, the second ultraviolet absorber is liquid at room temperature, and the content of the second ultraviolet absorber is 1 to 10 times the content of the first ultraviolet absorber. [Configuration 9] A reflective display device according to Configuration 8, wherein the second ultraviolet absorber is a benzotriazole derivative. [Configuration 10] A reflective display device according to any one of Configurations 1 to 9, wherein the illumination unit has a touch panel on the viewing side, and the block layer is arranged on either the viewing side of the touch panel or the illumination unit side. [Configuration 11] A reflective display device according to any one of Configurations 1 to 10, wherein the reflective device is a reflective electronic paper display. [Configuration 12] A reflective display device according to any one of Configurations 1 to 10, wherein the reflective device is a reflective liquid crystal display.

[0103] 10 Reflective device, 12 Illumination unit, 14 Blocking layer, 16 Touch panel, 18 Low-reflection layer, 100, 102, 104, 106 Reflective display device, 200 Measuring instrument, 202 Illumination device, 204 Shielding curtain.

Claims

1. A reflective display device comprising: a reflective device; an illumination unit disposed on the viewing side of the reflective device and irradiating the reflective device with light; and a blocking layer that prevents or reduces the transmission of ultraviolet light or ultraviolet light and high-energy visible light in the wavelength range of 380 nm to 425 nm, wherein when the reflective device is set to display white, BLR ≤ 0.5 and BLTF ≤ 0.085 are satisfied in either the state when the illumination unit is lit or when the illumination unit is not lit under ambient light.

2. The reflective display device according to claim 1, characterized in that the block layer is arranged on the viewing side of the illumination unit.

3. A reflective display device according to claim 1 or 2, wherein the illumination unit comprises a light guide plate having an emitting surface facing the display surface of the reflective device and an incident surface intersecting the emitting surface, and a light source that incidents light on the incident surface.

4. A reflective display device according to claim 1 or 2, characterized in that the illumination unit includes an organic electroluminescent element comprising a first transparent substrate, an anode, an organic layer, a cathode arranged to form a periodic pattern, and a second transparent substrate facing the first transparent substrate, facing the viewing side.

5. A reflective display device according to claim 4, characterized in that the emission spectrum of the illumination unit has a ratio of the peak intensity around 450 nm to the peak intensity around 475 nm within the range of 1.1 to 1.45, and a color temperature of 5600 K or less.

6. A reflective display device according to claim 1, characterized in that the light transmittance of the block layer in the range of 380 nm to 405 nm is 5% or less, and the maximum value of the light transmittance in the range of 405 nm to 425 nm is 90% or less.

7. A reflective display device according to claim 1 or 6, characterized in that the light transmittance of the block layer at 380 nm or less is 5% or less.

8. A reflective display device according to claim 6, wherein the block layer is an adhesive layer comprising an acrylic copolymer, a first ultraviolet absorber, and a second ultraviolet absorber, wherein the first ultraviolet absorber is a 2-phenylbenzotriazole derivative having a thioaryl ring group, the second ultraviolet absorber is liquid at room temperature, and the content of the second ultraviolet absorber is 1 to 10 times the content of the first ultraviolet absorber.

9. A reflective display device according to claim 8, characterized in that the second ultraviolet absorber is a benzotriazole derivative.

10. A reflective display device according to claim 1, characterized in that it has a touch panel on the viewing side of the illumination unit, and the block layer is arranged on either the viewing side of the touch panel or the illumination unit side.

11. A reflective display device according to claim 1, characterized in that the reflective device is a reflective electronic paper display.

12. A reflective display device according to claim 1, characterized in that the reflective device is a reflective liquid crystal display.

Images