Reflective display device

Abstract

To provide a reflective display device that maintains color accuracy and emits blue light below a certain standard in both outdoor and indoor environments. [Solution] A reflective display device comprising a reflective device 10, an illumination unit 12 positioned on the viewing side of the reflective device 10 and irradiating the reflective device 10 with light, and a blocking layer 14 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 10 is displayed in white, the conditions BLR ≤ 0.5 and BLTF ≤ 0.085 are satisfied in either the state when the illumination unit 12 is lit or when the ambient light illumination unit 12 is not lit.

Description

[Technical Field]

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

[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%. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2019-109429 [Patent Document 2] Japanese Patent Publication No. 2016-142942 [Patent Document 3] Japanese Patent Publication No. 2014-202864 [Overview of the Initiative] [Problems that the invention aims to solve]

[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 450nm as the light source for the front light of the light guide plate system. However, the light from this light source contains light with wavelengths of 380nm to 500nm, often referred to as blue light, raising concerns about eye strain.

[0008] EyeSafe standards are 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 shown in 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 CIE1931 RGB luminosity function. Furthermore, a scaling factor of 0.001 is used in the wavelength range of 700nm to 780nm.

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[0009] The standards state that a BLR of 0.5 or less and a BLTF of 0.085 or less are desirable.

[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, such as those described in Patent Documents 2 and 3, do not provide the desired effect.

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

[0013] However, the performance of the block layer depends on the incident angle of light, and there is a problem that the performance is not sufficient.

Means for Solving the Problems

[0014] One aspect of the present invention includes a reflective device, an illumination unit disposed on the viewing side of the reflective device for irradiating the reflective device with light, and a block layer that prevents or reduces the transmission of ultraviolet light or ultraviolet light and high-energy visible light in a wavelength range of 380 nm to 425 nm. When the reflective device is white-displayed, BLR≤0.5 and BLTF≤0.085 are satisfied in any of the states when the illumination unit is lit and when the illumination unit is not lit under external light. The reflective display device is characterized by this.

[0015] Here, it is preferable that the block layer is disposed on the viewing side of the illumination unit.

[0016] Further, it is preferable that the illumination unit includes a light guide plate having an emission surface facing the display surface of the reflective device and an incident surface intersecting the emission surface, and a light source that emits light to the incident surface.

[0017] Further, it is preferable that the illumination unit includes an organic electroluminescence element including a first transparent substrate, an anode, an organic layer, a cathode disposed to form a periodic pattern, and a second transparent substrate facing the first transparent substrate on the viewing side.

[0018] Further, it is preferable that the emission spectrum of the illumination unit has a ratio of the peak intensity near 450 nm to the peak intensity near 475 nm within a range of 1.1 to 1.45 and a color temperature of 5600 K or less.

[0019] Further, it is preferable that 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 at more than 405 nm and 425 nm or less is 90% or less.

[0020] Furthermore, it is preferable that the light transmittance of the block layer below 380 nm 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. [Effects of the Invention]

[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. [Brief explanation of the drawing]

[0027] [Figure 1] This is a schematic cross-sectional view showing an example of the configuration of a reflective display device in an embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view showing an example of the configuration of a reflective display device in an embodiment of the present invention. [Figure 3]This is a schematic cross-sectional view showing an example of the configuration of a reflective display device in an embodiment of the present invention. [Figure 4] This is a schematic cross-sectional view showing an example of the configuration of a reflective display device in an embodiment of the present invention. [Figure 5] This figure shows the spectral characteristics of the direct-emitting OLED used in the example. [Figure 6] This figure shows the wavelength dependence of the transmittance of the optical adhesive layer used as a block layer in an embodiment of the present invention. [Figure 7] This figure shows the radiance measurement status in the examples and comparative examples. [Figure 8] This figure shows a table summarizing the evaluation results of the examples and comparative examples of the present invention. [Figure 9] This figure shows the wavelength dependence of Comparative Example 1-1 by normalized intensity in the wavelength range of 380nm to 780nm, and the wavelength dependence of Comparative Example 1-1 by blue light hazard function in the same wavelength range. [Figure 10] This figure shows the wavelength dependence of the 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 500 nm. [Figure 11] This figure shows the wavelength dependence of the 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. [Figure 12] This figure shows the wavelength dependence of the 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. [Figure 13] This figure shows the wavelength dependence of Comparative Example 5-1 by normalized intensity in the wavelength range of 380nm to 780nm, and the wavelength dependence of Comparative Example 5-1 by blue light hazard function in the same wavelength range. [Figure 14]This figure shows the wavelength dependence of the 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. [Modes for carrying out the invention]

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

[0029] The reflective device 10 is a component of the reflective display device 100 that has a display function. The reflective device 10 can be, for example, a reflective electronic paper display or a reflective liquid crystal display.

[0030] The illumination unit 12 is a component that has the function of illuminating the reflective device 10, which is called a front light. In the reflective display device 100, the illumination unit 12 is positioned on the viewing side (the side where the user views the display) of the reflective device 10.

[0031] The illumination unit 12 can be configured to include, for example, an emission surface facing the display surface of the reflective device 10 and a light guide plate having an incidence surface intersecting the emission surface. Alternatively, the illumination unit 12 can be configured to include, for example, an organic electroluminescent element including a first transparent substrate, an anode, an organic layer, a cathode arranged with a periodic pattern, and a second transparent substrate facing the first transparent substrate, facing the viewing side of the reflective display device 100.

[0032] When the illumination unit 12 includes an organic electroluminescent element, it is preferable that it exhibits an emission spectrum having two peaks around 450 nm and 475 nm. Here, "around 450 nm" refers to the wavelength range of 440 nm to 460 nm. Also, "around 475 nm" refers to the wavelength range of 465 nm to 485 nm. The illumination unit 12 is preferably configured to have a light source with a color temperature of 5600 K or less by adjusting the ratio of the peak intensity around 450 nm to the peak intensity around 475 nm between 1.1 and 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). When used as an illumination unit for a reflective device, a color temperature of over 4000 K and up to 5600 K is more preferable from the viewpoint of preventing the display screen from becoming reddish.

[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 underneath. 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 380nm to 425nm 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 425nm. Specifically, it is preferable that the blocking layer 14 has a light transmittance of 5% or less in the 380nm to 405nm range, and a maximum light transmittance of 90% or less in the range between 405nm and 425nm. It is also preferable that the blocking layer 14 has a light transmittance of 5% or less below 380nm.

[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 in the reflective display device 100 that has a function for detecting the location touched by the user or the location the user has approached. The touch panel 16 can be, for example, a capacitive touch panel. A capacitive touch panel is constructed by laminating a plurality of first electrodes, which extend in the X direction and are arranged in a line along the Y direction intersecting the X direction, and a plurality of second electrodes, which extend in the Y direction and are arranged in a line along the X direction, with an insulating layer in between. The first and 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. The first and second electrodes are preferably made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). In such a configuration, it is possible to detect the location touched by the user or the location the user has approached by detecting the Y-direction position of the first electrode and the X-direction position of the second electrode, where the capacitance has changed.

[0037] In the reflective display device 100, the touch panel 16 is provided on the viewing side of the block layer 14. However, as shown in Figure 2, a configuration like the 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, is also possible.

[0038] Furthermore, as shown in Figure 3, a configuration such as the reflective display device 104 without a touch panel 16 may be used. Also, as shown in Figure 4, a configuration such as the reflective display device 106 in which a block layer 14 is provided on the reflective device 10 side of the illumination unit 12 may be used. Note that even in configurations with a touch panel 16, such as the reflective display devices 100 and 102, a configuration in which a block layer 14 is provided on the reflective device 10 side of the illumination unit 12 may be used.

[0039] The low-reflection layer 18 is a component that has 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, silicon oxide (SiO2) and titanium oxide (TiO2) can be used for the low-reflection layer 18.

[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 by formula (1) above is 0.5 or less and the BLTF shown by formula (2) above is 0.085 or less.

[0042] By satisfying these conditions, it is possible to attenuate the light in the wavelength range of blue light to a safe reference level among the reflected light of the light emitted from the lighting unit 12 to the reflective device 10 and the leakage light to the observer side in the case of the lighting unit 12 using the light guide plate method. Further, when there is external light such as sunlight and the lighting unit 12 is not used, after attenuating the blue light contained in the external light and sunlight, by observing the reflected light thereof, the reflective display device 100 can be used with safety while maintaining visibility.

[0043] In addition, since the blocking layer 14 attenuates ultraviolet rays and high-energy visible rays, in the case of a reflective display device including an organic electroluminescence element, its durability can be enhanced.

[0044] In addition, ΔE, which is an index of color change, is obtained from the measured values of L * , a * and b * using a spectro-radiance meter with the measured value of the standard white plate as a reference. ΔE is an index that numerically represents the color difference and is mainly used to evaluate the color change and color matching degree. By quantitatively representing the color difference, it shows how visually different the colors look. In the present invention, the evaluation criteria for ΔE are evaluated as ΔE ≤ 2: no color difference is felt, 2 < ΔE ≤ 7: a slight color difference is felt but not noticeable, 7 < ΔE: a color difference is felt. That is, if ΔE is 7 or less, it is evaluated that the color difference between the two reflective display devices is not noticeable and there is no visual problem.

[0045] ΔE, which is an index of color change, is obtained from the respective L * a * b * color space values obtained by measurement from two target samples using the following formula (3). (Equation 3) ΔE = √((L1 * - L2 * )^2 + (a1 * - a2 * )^2 + (b1 * - b2 * )^2) ···(3)

[0046] In addition, the YI (Yellow Index), which is an index of yellowness, is obtained from the following formula (4) defined in JIS K7373 for the tristimulus values XYZ measured by a spectro-radiance meter in an outdoor light simulation state using the daylight light source D65. It is said that the smaller the numerical value, the less yellowing. In the present invention, the evaluation criteria for YI are as follows: 7 < YI ≤ 30: little yellowing, 5 < YI ≤ 7: considerably little yellowing, YI ≤ 5: extremely little yellowing. That is, if YI is 30 or less, it is evaluated that the yellowing of the reflective display device is visually not problematic. (Equation 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, for each of the examples and comparative examples, when the reflective device was set to white display, evaluations were performed under two conditions: "when the lighting unit is lit" and "when the lighting unit is not lit under outdoor light". To express this clearly, hereinafter, for each of the examples and comparative examples, when the lighting unit is lit after setting the reflective device to white display, the name with "-1" appended to the end of the name of each of the examples and comparative examples, and when the lighting unit is not lit after setting the reflective device to white display, the name with "-2" appended to the end of the name of each of the examples and comparative examples. For example, in the case of "Example 2" and "Comparative Example 3", when the lighting unit is lit after setting the reflective device to white display, they are referred to as "Comparative Example 2-1" and "Comparative Example 3-1" in order, and when the lighting unit is not lit after setting the reflective device to white display, they are referred to as "Comparative Example 2-2" and "Comparative Example 3-2" in order.

[0048] In addition, in the examples and comparative examples, evaluations were performed with the configuration of the reflective display device 104 in FIG. 3. However, in Comparative Examples 1, 3, and 5, no block layer was used in the configuration.

[0049] In Examples 1 and 2 and Comparative Examples 1 to 4, the reflective device was an EPD (Electronic Printed Display). 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 Inc.

[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 serves as the front light, was a direct-emitting OLED. The direct-emitting 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 450nm (hereinafter referred to as the normalized intensity) is 1 and the normalized intensity around 475nm 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 450nm is 0.648 and the normalized intensity around 475nm 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 (Blue Light Frequency Factor) 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," a 100 μm thick adhesive of the ultraviolet and high-energy visible light absorbing type 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 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 below 380 nm, 5% or less between 380 nm and 405 nm, and a maximum transmittance of 0.990% or less 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 used, the measurement was performed in a darkroom with the measuring instrument 200 positioned on the normal to the display surface of the reflective display device 104. 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 to perform the measurements 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 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 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, no block layer was provided, and a light guide plate system was used for the illumination section. However, the BLR was 0.54 and the BLTF was 0.086. In other words, neither the BLR of 0.5 or less (the standard) nor the BLTF of 0.085 or less (the standard) was met.

[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 absorption and high-energy visible light absorption 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 Disc) 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-illuminated 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 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-illuminated 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 a direct-illuminating 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, it was possible to satisfy the standard BLR of 0.5 or less and the standard BLTF of 0.085 or less.

[0080] However, in Comparative Example 3-2, which was evaluated under ambient light simulation conditions with the direct-illuminated 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, resulting in a BLR of 0.28 and a BLTF of 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-illuminated 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 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 0.29 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.

[0088] Furthermore, in Example 3-2, which is an evaluation under ambient light simulation conditions where the direct-illuminated 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 meet the standard of 0.5 or less and the BLTF was able to meet 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-illumination 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, it was possible to satisfy the standard BLR of 0.5 or less and the standard BLTF of 0.085 or less.

[0090] However, in Comparative Example 5-2, which was evaluated under ambient light simulation conditions with the direct-illuminated 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 was applied as the reflective device and adhesive 1, which is of the ultraviolet absorbing and high-energy visible light absorbing type, was 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 1-3 and Comparative Examples 1-6, the 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 1-2 in Example 1: YI value "21.6" Example 2-2 in Example 2: YI value "5.8" Example 3-2 in Example 3: 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, adhesive 1, which is of the ultraviolet-absorbing and high-energy visible light-absorbing type, was applied to the block layer, and either a light guide plate system or a direct-illuminating 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 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 device 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 kept below 5600 K (e.g., 4000 K) even if the blocking 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 blocking layer that absorbs ultraviolet light and high-energy visible light.

[0099] Furthermore, in the reflective display device configurations of Examples 2 and 3, where the block layer is located on the viewing side of the illumination unit, degradation of the organic layer of the direct-emitting OLED, which is the illumination unit, due to short-wavelength light irradiation can be suppressed, and the luminous efficiency can be maintained over a long period of time. In other words, when a direct-emitting 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] [Structure of the present invention] [Configuration 1] Reflective devices and An illumination unit is positioned on the viewing side of the reflective device and irradiates the reflective device with light, 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 380nm to 425nm, Equipped with, A reflective display device characterized in that, 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 as described in Configuration 1, The reflective display device is characterized in that the block layer is arranged on the viewing side of the illumination unit. [Configuration 3] A reflective display device according to configuration 1 or 2, The illumination unit includes a light guide plate having an emission surface facing the display surface of the reflective device and an incidence surface intersecting the emission surface, A light source that incidents light on the incident surface, A reflective display device characterized by having the following features. [Structure 4] A reflective display device according to configuration 1 or 2, The illumination unit is characterized by including an organic electroluminescent element that includes 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. [Composition 5] A reflective display device as described in configuration 4, The reflective display device is 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 the color temperature is 5600 K or less. [Composition 6] A reflective display device according to any one of configurations 1 to 5, A reflective display device characterized in that the light transmittance of the block layer in the 380nm to 405nm range is 5% or less, and the maximum value of the light transmittance in the range from 405nm to 425nm is 90% or less. [Composition 7] A reflective display device according to any one of configurations 1 to 6, A reflective display device characterized in that the light transmittance of the block layer below 380 nm is 5% or less. [Structure 8] A reflective display device according to configuration 6 or 7, The block layer is an adhesive layer comprising 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 UV absorber is liquid at room temperature. A reflective display device characterized in that the content of the second ultraviolet absorber is 1 to 10 times the content of the first ultraviolet absorber. [Composition 9] A reflective display device as described in configuration 8, The reflective display device is characterized in that the second ultraviolet absorber is a benzotriazole derivative. [Configuration 10] A reflective display device according to any one of items 1 to 9, The lighting unit has a touch panel on the viewing side, A reflective display device characterized in that the block layer is arranged on either the viewing side or the illumination side of the touch panel. [Composition 11] A reflective display device according to any one of the configurations 1 to 10, The reflective device is a reflective electronic paper display, characterized in that it is a reflective display device. [Composition 12] A reflective display device according to any one of the configurations 1 to 10, The reflective device is a reflective liquid crystal display, characterized in that it is a reflective display device. [Explanation of symbols]

[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. Reflective devices and An illumination unit is positioned on the viewing side of the reflective device and irradiates the reflective device with light, 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, Equipped with, When the reflective device is set to white, in either the state when the illumination unit is lit or when the illumination unit is not lit under ambient light, BLR ≤ 0.5 and BLTF ≤ 0.085 are satisfied. The illumination unit includes an organic electroluminescent element comprising, facing the viewing side, 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. The reflective display device is 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 the color temperature is 5600 K or less.

2. A reflective display device according to claim 1, The reflective display device is 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, A reflective display device 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.

4. A reflective display device according to claim 1 or 3, A reflective display device characterized in that the light transmittance of the block layer at 380 nm or less is 5% or less.

5. A reflective display device according to claim 3, The block layer is an adhesive layer comprising 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 liquid at room temperature. A reflective display device characterized in that the content of the second ultraviolet absorber is 1 to 10 times the content of the first ultraviolet absorber.

6. A reflective display device according to claim 5, The reflective display device is characterized in that the second ultraviolet absorber is a benzotriazole derivative.

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

8. A reflective display device according to claim 1, The reflective device is a reflective electronic paper display, characterized in that it is a reflective display device.

9. A reflective display device according to claim 1, The reflective device is a reflective liquid crystal display, characterized in that it is a reflective display device.

Images