Optical filters

Abstract

An optical filter with a light-absorbing layer formed by mixing several dyes on a transparent substrate, wherein the light-absorbing layer comprises: a first light-absorbing dye for the absorption of blue light in the wavelength range of 435 nm to 460 nm; and a second light-absorbing dye for the absorption of orange-red light in the wavelength range of 580 nm to 640 nm with an average wavelength absorption rate of more than 15%.

Description

CROSS-REFERENCE TO RELATED REGISTRATIONS

[0001] This disclosure claims priority over Taiwanese patent application no. 114103074, filed on January 23, 2025. TECHNICAL AREA

[0002] The present disclosure relates to the technology of blue light filtering and in particular to an optical filter which enables a high reduction of blue light toxicity while maintaining display performance. BACKGROUND

[0003] Reference is made to US patent application No. 19 / 222,339, which discloses an absorption in the orange-red wavelength range from 580 nm to 620 nm with a center wavelength between 590 nm and 610 nm to achieve direct color temperature compensation and thereby enable improved blue light blocking while maintaining the display without color deviation.

[0004] Fig. Figure 1 shows a schematic diagram of the light source waveforms of LCD and OLED backlight modules. As can be seen from Fig. As can be seen in Figure 1, the orange-red light source waveform of an LCD backlight module has a maximum at approximately 600 nm, while the orange-red light source waveform of an OLED backlight module has a maximum at approximately 620 nm. Therefore, the inventor decided to conduct experiments based on the aforementioned application to test whether an anti-blue light filter could be developed that is universally suitable for different backlight modules while maintaining good display quality. SUMMARY OF THE REVELATION

[0005] One aspect of the present disclosure is to provide an optical filter that is universally applicable to different backlight modules and enables a high reduction in blue light toxicity while maintaining display performance.

[0006] In one embodiment, the optical filter comprises a light-absorbing layer formed by mixing several dyes on a transparent substrate. The light-absorbing layer includes a first light-absorbing dye and a second light-absorbing dye. The first light-absorbing dye absorbs blue light in the wavelength range of 435 nm to 460 nm. The second light-absorbing dye absorbs orange-red light in the wavelength range of 580 nm to 640 nm with an average wavelength absorption rate of at least 15%.

[0007] In another embodiment, the first light-absorbing dye absorbs blue light with an absorption rate of at least 50% in the wavelength range of 435 nm to 440 nm, or absorbs 30% to 50% in the range of 435 nm to 440 nm and absorbs more than 10% blue light in the wavelength range of 450 nm to 460 nm.

[0008] Direct color temperature compensation is achieved through absorption in the orange-red wavelength range of 580 nm to 640 nm, with the absorption rate in this wavelength range set to at least 15%, so that the optical filter has both high blue light blocking and the maintenance of display performance and is universally applicable for LCD and OLED backlight modules. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows a schematic diagram of the light source waveforms of LCD and OLED backlight modules. Fig. Figure 2 shows an exemplary spectrum according to an embodiment of the present disclosure. Fig. Figure 3 shows an exemplary spectrum according to a further embodiment of the present disclosure. Fig. Figure 4 shows an exemplary spectrum according to further embodiments of the present disclosure. Fig. Figure 5 shows an exemplary spectrum according to a further embodiment of the present disclosure. DETAILED DESCRIPTION

[0009] With reference to Fig. Figure 2 shows a spectral diagram illustrating an embodiment of the optical filter according to the present disclosure. This embodiment comprises a light-absorbing layer formed by coating a transparent substrate with several dyes in combination, the light-absorbing layer containing a first light-absorbing dye and a second light-absorbing dye as its main components.

[0010] For clarity, the spectra shown in the accompanying figures are based on light transmission measurements. When incident light from a light source passes through the transparent substrate, absorption and transmission are inversely proportional; for example, an absorption rate of 60% corresponds to a transmission of 40%. In this embodiment, the first light-absorbing dye exhibits absorption rates of 80% to 90% for blue light in wavelength range 20 (435 nm to 440 nm), corresponding to transmission values ​​of 20% to 10%. The second light-absorbing dye is directed toward orange-red light in wavelength range 22 (580 nm to 640 nm). The introduction of orange-red light-absorbing dyes results in a controlled color temperature shift. In this configuration, the color temperature shift relative to the original light source is limited to within 500 K.For example, when light with a color temperature of 6500 K passes through the filter system, the color temperature is first reduced to approximately 5000 K by attenuating the blue light using the first light-absorbing dye. The second light-absorbing dye then provides a compensating correction through the selective absorption of orange-red wavelengths, restoring the color temperature to approximately 6000 K to 6500 K.

[0011] As in Fig. As shown in Figure 2, the second light-absorbing dye exhibits absorption properties in the orange-red wavelength range 22 (580 nm–640 nm) with average absorption rates of more than 25%, corresponding to a transmission of 75%. This absorption profile strategically encompasses both the emission peak at 600 nm (waveform 10) characteristic of LCD backlight systems and the emission peak at 620 nm (waveform 12) typical of OLED backlight systems, enabling the optical filter to provide superior display performance in both LCD and OLED applications.

[0012] Nevertheless, achieving optimal display quality requires understanding that minimizing color temperature deviation alone does not guarantee the elimination of perceptible color differences. Although the second light-absorbing dye provides effective color temperature compensation, human visual perception exhibits wavelength-dependent sensitivity differences. Therefore, identical color temperatures can still produce distinguishable visual appearances due to underlying differences in spectral distribution, a phenomenon known as color tolerance or metameric color difference.

[0013] Experimental results conducted by the inventor showed that, despite the absorption of orange-red light by the second light-absorbing dye, the compensated white color exhibited perceptible color deviations at a color temperature of 6000 K to 6500 K compared to the original spectrum. To remedy this problem, the light-absorbing layer contains a third light-absorbing dye, which is directed towards the green light wavelength range of 520 nm to 580 nm and exhibits maximum absorption peaks in the range of 10% to 40%.

[0014] The visible light spectrum for human vision typically ranges from 380 nm to 780 nm, with the violet-blue range (380 nm to 410 nm) having the highest energy content, followed by the blue light range. While blue light wavelengths from 400 nm to 500 nm are known to cause photochemical damage to the human eye, the violet-blue light spectrum from 380 nm to 410 nm is of particular concern due to its proximity to ultraviolet A radiation and its correspondingly higher energy levels. This high-energy radiation has a significant ability to penetrate the dermis, reaching the dermal layer where it breaks down collagen and elastic fibers and generates harmful free radicals. These effects accelerate skin aging processes and stimulate melanin production.Consequently, the first light-absorbing dye is designed to not only absorb blue light in the range of 435 nm to 440 nm, but also 90% to 100% (corresponding to 10% to 0% transmission) of violet-blue light in the wavelength range 24 from 380 nm to 410 nm.

[0015] The specified absorption wavelength ranges of the aforementioned light-absorbing dyes represent optimal absorption ranges in which each material exhibits its peak performance characteristics. It should be understood that spectral absorption extends beyond these primary ranges, producing overlapping absorption effects across the spectrum. The specified absorption rates can be achieved with single-component materials or through synergistic combinations of multiple light-absorbing compounds. For example, the first light-absorbing dye, which is targeted at blue wavelengths, may comprise a mixture of two or more different light-absorbing particle materials to achieve the desired spectral response.

[0016] Given the differing spectral properties of various display technologies, with OLED backlight sources exhibiting blue light emission peaks at approximately 455 nm and LCD backlight sources showing peaks near 444 nm, the absorption profile of the first light-absorbing dye can be strategically optimized. Specifically, the absorption rate in the wavelength range of 435 nm to 440 nm can be reduced while simultaneously increasing the absorption of blue light in the region around 455 nm, thereby improving the filter's effectiveness against OLED-specific blue light emissions. This optimization allows the first light-absorbing dye to be configured with absorption rates below 50% (typically 30% to 50%) in the 435 nm to 440 nm range, while maintaining absorption rates greater than 10% within any wavelength band between 450 nm and 460 nm.

[0017] With reference to Fig. 3 Another embodiment of the optical filter is illustrated by a spectral diagram. This embodiment differs from the one described in Fig. The profile shown in Figure 2 is primarily determined by the absorption properties of the second light-absorbing dye. In this embodiment, the second light-absorbing dye has an average absorption rate of more than 30% and exhibits a characteristic two-region absorption profile comprising a peak-valley section and a flat section. The peak-valley section, extending from 580 nm to 600 nm, has a center wavelength with a full width at half maximum (FWHM) of 10 nm to 20 nm. This region corresponds to the LCD emission peak of the orange-red light 22, with maximum absorption occurring between 590 nm and 595 nm at rates exceeding 40%. The flat section extends from 600 nm to 640 nm, corresponds to the OLED emission peak of the orange-red light 22, and exhibits absorption rates exceeding 20%. The width of the flat section can range from 30 nm to 60 nm.

[0018] In this context, the "flat section" is defined as the area in which the difference between the maximum and minimum absorption values ​​lies within plus or minus 5%.

[0019] The experimental results for this embodiment, as in Fig. Figure 3 shows optimal performance characteristics. The first light-absorbing dye achieves an absorption rate of more than 80% in the blue light wavelength range near 435 nm. The second light-absorbing dye exhibits peak absorption between 590 nm and 595 nm and attenuates approximately 40% to 50% of the incident orange-red light in the wavelength range 22 (corresponding to a minimum transmission valley of approximately 60% to 50%), with the width of the flat section ranging from 30 nm to 60 nm. The third light-absorbing dye shows maximum absorption at 550 nm within the range of 520 nm to 580 nm and absorbs approximately 35% of the green light in the wavelength range 26 (corresponding to a minimum transmission valley of approximately 65%).This synergistic combination effectively reduces blue light hazards while maintaining high optical clarity with a total transmission of more than 80% and white balance characteristics that closely approximate natural color reproduction.

[0020] With reference to Fig. Figure 4 illustrates another embodiment of the optical filter with reference to a spectrum. In this embodiment, the first light-absorbing dye exhibits absorption rates of at least 50% for blue light in the wavelength range 20 (435 nm to 440 nm), corresponding to transmission values ​​of approximately 35% to 50%. While maintaining a color temperature deviation within 500 K, the second light-absorbing dye shows high absorption efficiency and attenuates more than 20% of the orange-red light in the wavelength range 22 (580 nm to 640 nm), which correlates with a transmission of less than 80%. The third light-absorbing dye causes moderate absorption of 20% to 25% for green light in the wavelength range 26 (520 nm to 580 nm), corresponding to transmission values ​​of 75% to 80%.

[0021] With reference to Fig.Figure 5 shows another embodiment of the optical filter. This variant exhibits similar blue light absorption properties, with the first light-absorbing dye absorbing more than 50% of the blue light in the wavelength range 20 (435 nm to 440 nm), corresponding to approximately 35% to 50% transmission. Color temperature stability is maintained within a deviation of 500 K by the second light-absorbing dye, which has an average absorption rate of more than 20% and exhibits a bimodal absorption profile. The absorption spectrum includes a peak-trough region from 580 nm to 600 nm with a center wavelength that has a full width at half maximum (FWHM) of 10 nm to 20 nm. This region targets the LCD emission characteristics, with peak absorption between 590 nm and 595 nm exceeding 30% and corresponding to the orange-red light range 22.The flat section extends from 600 nm to 640 nm and specifically addresses the OLED emission characteristics in the orange-red light range 22, where the absorption rates are more than 10% and the width of the flat section can be in the range of 30 nm to 60 nm.

[0022] Accordingly, the optical filter and associated optical shield described herein offer comprehensive blue light reduction through systematic spectral design. The optimal absorption properties of the first light-absorbing dye in the 430 nm to 460 nm range are determined based on the transmission requirements specified in the disclosure. Color temperature compensation is achieved by targeted absorption of orange-red light (580 nm to 640 nm) within acceptable deviation limits of 350 K to 500 K. By maintaining absorption rates of the second light-absorbing dye of more than 15% in the specified wavelength range, the optical filter achieves a dual function: effective reduction of blue light hazard and preservation of display quality.This design approach enables universal compatibility across LED and OLED backlight technologies and provides versatile solutions for different display technologies. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] TW 114103074

[0001]

Claims

[1] An optical filter with a light-absorbing layer formed by mixing several dyes on a transparent substrate, wherein the light-absorbing layer comprises: a first light-absorbing dye for the absorption of blue light in the wavelength range of 435 nm to 460 nm; and a second light-absorbing dye for the absorption of orange-red light in the wavelength range of 580 nm to 640 nm with an average wavelength absorption rate of more than 15%. [2] An optical filter according to claim 1, wherein the second light-absorbing dye has an average absorption rate of more than 15% and contains an absorption flat area with a width between 30 and 60 nm. [3] An optical filter according to claim 1 or 2, wherein the second light-absorbing dye has a maximum absorption rate of more than 25% and contains an absorption flat region with a width between 30 and 60 nm. [4] An optical filter according to any one of claims 1 to 3, wherein the absorption profile of the second light-absorbing dye has a peak-valley region and a flat region between 580 nm and 640 nm, wherein the peak-valley region has a mid-wavelength between 580 nm and 600 nm and the flat region lies between 600 nm and 640 nm. [5] An optical filter according to claim 4, wherein: the peak-trough region exhibits an absorption maximum between 590 nm and 595 nm with an absorption rate of more than 40%; and The flat region between 600 nm and 640 nm has an absorption rate of more than 20%. [6] An optical filter according to claim 4, wherein: the peak-trough region exhibits an absorption maximum between 590 nm and 595 nm with an absorption rate of more than 30%; and The flat region between 600 nm and 640 nm has an absorption rate of more than 10%. [7] An optical filter according to any one of claims 1 to 6, further comprising a third light-absorbing dye for the absorption of more than 10% of green light between 520 nm and 580 nm. [8] An optical filter according to any one of claims 1 to 7, wherein the first light-absorbing dye absorbs at least 50% of the blue light in the wavelength range of 435 nm to 440 nm. [9] An optical filter according to any one of claims 1 to 8, wherein the first light-absorbing dye absorbs 30% to 50% of the blue light between 435 nm and 440 nm and absorbs more than 10% of the blue light in the wavelength range of 450 nm to 460 nm. [10] An optical filter according to any one of claims 1 to 9, wherein the first light-absorbing dye further absorbs more than 90% of the violet-blue light in the wavelength range of 380 nm to 410 nm.

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