Abstract

All glass, lenticular lens array, light guide substrates were fabricated in a single mask and etch procedure enabling 1D local light-confinement from an edge-injected LED array. Lenticular structures of sufficient resolution (width & pitch: 100–200 µm) were etched along the length of the thin-slab glass surface, at depths in the range 40–90 µm using an etchant optimized for the alkali-borosilicate composition (Corning Iris Glass). These structures’ aspect ratio (W/H < 3) and pitch effectively controlled the degree of light confinement (local dimming index (LDI) > 80%) along the lenticular corridors. The all-glass and high-transmission nature of the iris glass composition enabled higher brightness operation and yielded negligible color-shift.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

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References

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  1. D. Yi, “Display Light Guide Plate (LGP) Report – 2013,” IHS Electronics & Media market, technology and supply chain analysis, (2013).
  2. P. de Greef and H. Groot-Hulze, “39.1 Adaptive dimming and boosting backlight for LCD-TV systems,” Society for Information Display Symposium Digest of Technical Papers: 38(1), 1332–1335 (2007).
    [Crossref]
  3. S. Cha, T. Choi, H. Lee, and S. Sull, “An Optimized Backlight Local Dimming Algorithm for Edge-Lit LED Backlight LCDs,” J. Disp. Technol. 11(4), 378–385 (2015).
    [Crossref]
  4. X. Mi, K. Allen, D. Kuksenkov, J. Tokar, A. Sullivan, and S. Rosenblum, “Patterned holey glass LGP based ultra-thin 2D local dimming backlight” Society for Information Display Symposium Digest of Technical Papers 14(1), 145–148 (2018).
  5. S. Jung, M. Kim, D. Kim, and J. Lee, “Local Dimming Design and Optimization for Edge-Type LED Backlight Unit,” Society for Information Display Symposium Digest of Technical Papers, pp.1430–1432 (2011).
    [Crossref]
  6. Y. C. Kim, H. D. Im, M. G. Lee, and H. Y. Choi, “Directivity Enhanced BLU for Edge-type Local Dimming”, Society for Information Display Symposium Digest of Technical Papers, pp.662- 664 (2011).
    [Crossref]
  7. K. Käläntär, “A directional backlight with narrow angular luminance distribution for widening the viewing angle for an LCD with a front-surface light-scattering film,” J. Soc. Inf. Disp. 20(3), 133 (2012).
    [Crossref]
  8. T. Teng,and L. Tseng, “Effect of a light guide plate with lenticular-arrayed surface on optical output for backlight and illumination”, Proc. SPIE 8835, LED-based Illumination Systems, 88350H (30 September 2013).
  9. M. Isshiki, Y. Arai, M. Inoue, T. Sasaki, and K. Käläntär, “Monolithic Glass Light-Guide Plate with Built-in Prism Structure for 1D Dimming Large-Area LCD,” Society for Information Display Symposium Digest of Technical Papers, pp.149- 152 (2018).
    [Crossref]

2015 (1)

S. Cha, T. Choi, H. Lee, and S. Sull, “An Optimized Backlight Local Dimming Algorithm for Edge-Lit LED Backlight LCDs,” J. Disp. Technol. 11(4), 378–385 (2015).
[Crossref]

2012 (1)

K. Käläntär, “A directional backlight with narrow angular luminance distribution for widening the viewing angle for an LCD with a front-surface light-scattering film,” J. Soc. Inf. Disp. 20(3), 133 (2012).
[Crossref]

Cha, S.

S. Cha, T. Choi, H. Lee, and S. Sull, “An Optimized Backlight Local Dimming Algorithm for Edge-Lit LED Backlight LCDs,” J. Disp. Technol. 11(4), 378–385 (2015).
[Crossref]

Choi, T.

S. Cha, T. Choi, H. Lee, and S. Sull, “An Optimized Backlight Local Dimming Algorithm for Edge-Lit LED Backlight LCDs,” J. Disp. Technol. 11(4), 378–385 (2015).
[Crossref]

Käläntär, K.

K. Käläntär, “A directional backlight with narrow angular luminance distribution for widening the viewing angle for an LCD with a front-surface light-scattering film,” J. Soc. Inf. Disp. 20(3), 133 (2012).
[Crossref]

Lee, H.

S. Cha, T. Choi, H. Lee, and S. Sull, “An Optimized Backlight Local Dimming Algorithm for Edge-Lit LED Backlight LCDs,” J. Disp. Technol. 11(4), 378–385 (2015).
[Crossref]

Sull, S.

S. Cha, T. Choi, H. Lee, and S. Sull, “An Optimized Backlight Local Dimming Algorithm for Edge-Lit LED Backlight LCDs,” J. Disp. Technol. 11(4), 378–385 (2015).
[Crossref]

J. Disp. Technol. (1)

S. Cha, T. Choi, H. Lee, and S. Sull, “An Optimized Backlight Local Dimming Algorithm for Edge-Lit LED Backlight LCDs,” J. Disp. Technol. 11(4), 378–385 (2015).
[Crossref]

J. Soc. Inf. Disp. (1)

K. Käläntär, “A directional backlight with narrow angular luminance distribution for widening the viewing angle for an LCD with a front-surface light-scattering film,” J. Soc. Inf. Disp. 20(3), 133 (2012).
[Crossref]

Other (7)

T. Teng,and L. Tseng, “Effect of a light guide plate with lenticular-arrayed surface on optical output for backlight and illumination”, Proc. SPIE 8835, LED-based Illumination Systems, 88350H (30 September 2013).

M. Isshiki, Y. Arai, M. Inoue, T. Sasaki, and K. Käläntär, “Monolithic Glass Light-Guide Plate with Built-in Prism Structure for 1D Dimming Large-Area LCD,” Society for Information Display Symposium Digest of Technical Papers, pp.149- 152 (2018).
[Crossref]

D. Yi, “Display Light Guide Plate (LGP) Report – 2013,” IHS Electronics & Media market, technology and supply chain analysis, (2013).

P. de Greef and H. Groot-Hulze, “39.1 Adaptive dimming and boosting backlight for LCD-TV systems,” Society for Information Display Symposium Digest of Technical Papers: 38(1), 1332–1335 (2007).
[Crossref]

X. Mi, K. Allen, D. Kuksenkov, J. Tokar, A. Sullivan, and S. Rosenblum, “Patterned holey glass LGP based ultra-thin 2D local dimming backlight” Society for Information Display Symposium Digest of Technical Papers 14(1), 145–148 (2018).

S. Jung, M. Kim, D. Kim, and J. Lee, “Local Dimming Design and Optimization for Edge-Type LED Backlight Unit,” Society for Information Display Symposium Digest of Technical Papers, pp.1430–1432 (2011).
[Crossref]

Y. C. Kim, H. D. Im, M. G. Lee, and H. Y. Choi, “Directivity Enhanced BLU for Edge-type Local Dimming”, Society for Information Display Symposium Digest of Technical Papers, pp.662- 664 (2011).
[Crossref]

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Figures (8)

Fig. 1
Fig. 1 (Left) Architecture of the conventional edge-lit backlight module in an LCD-LED TV. (Right) Schematic illustration of an LGP structure used to confine edge-lit illumination into one dimensional linear corridors.
Fig. 2
Fig. 2 (Left) Lenticular Structures (side view) – Various forms found suitable for 1D light confinement are shown above, with the height of the surface structures (H), their widths (W), and gaps (G) indicated. (Right) Ray Tracing (top view of LGP) - Light propagation in a LGP with lenticular structures are illustrated using a Lambertian ray source.
Fig. 3
Fig. 3 Overview of “Mask and “Etch” process individual steps - Iris glass substrate was cut-chamfered, cleaned (40kHz ultrasonic agitation 2% Semiclean KG, Linda Yokohama Oils & Fats Industry, Yokohama, Japan), and baked-stored at 200°C to drive off physisorbed interfacial water, prior to screen printing the etch mask. A stainless steel 360 mesh was typically employed, with a string angle of 22°, and 15 µm emulsion thickness. The printing proceeded along the lenticular “grooves” longitudinal direction, and a post-bake thermal cure was promptly applied by inserting the printed substrate into a 140° oven for at least an hour. The cured substrate was either etched in a bath, or with a spray process described in the text. The residual cured screen mask remaining on the substrate was sometimes removed towards the end of the etch procedures, or with a final clean procedure employing the screen mask solvent and acidic detergent.
Fig. 4
Fig. 4 SEM image (100 x) of screen optimized for producing high LDI “smooth” wall lenticular LGPs – The screen used for this etch-mask application employed a stainless steel 360 mesh with 56 µm opening, string angle of 22°, and a 7-15 µm thick emulsion with the 150 µm wide lenticular pattern.
Fig. 5
Fig. 5 Schematic illustrating parameters used to calculate the LDI light confinement, zone width and straightness [7–9] from luminance measurement image data. Unless otherwise stated, we exclusively used local dimming zone widths ~150 mm.
Fig. 6
Fig. 6 (Top row) Collection of lenticular etched-pattern samples (side view) prepared by the “mask and etch” procedures described in this paper, whose SEM images are laid out, with increasing aspect ratio and height, from left to right. (Bottom row) The corresponding LDI measurement images (top view) and values are laid out beneath its associated lenticular etched-pattern. Samples with LDI values greater than 80% were deemed acceptable for commercial purposes, sufficiently equivalent in behavior with commercially available plastic sheet.
Fig. 7
Fig. 7 Tunable Topography - From Sinusoidal to “Flat Top” Morphology - (Left column): Lenticular LGP sample was prepared by etching Iris glass sample WS01760 using the an etch mask with no adhesion promotor. (Right Column): Lenticular LGP sample WS01340 was prepared in similar fashion differing only in the use of strong adhesion promotion.
Fig. 8
Fig. 8 Light Confinement is Compromised with Longitudinal Side-Wall ‘Scalloping’ with Sharp Asperities – SEM images of two samples with different side wall smoothness were prepared from equivalent regions in the etched lenticular array LGPs, and shown above in the top row. The top left SEM image (100-X) illustrates the relatively smoother-walled sample WS01760 prepared with no adhesion promoter (ESTS-3000), contrasted with the top right SEM image (150-X) of sample WS01072 prepared with an additional adhesion promotion, prior to application of the CGSN etch-mask. Below each SEM image is the related luminance image used to measure the light confinement parameter: LDI. The LDI value for the “smooth” walled sample on the left was ~85% while the LDI value for the “kinked-tube” shaped lenticulars on the right were well below 65%.

Tables (2)

Tables Icon

Table 1 - Matrix of Different Etchant Baths explored for optimal IRIS glass etch rate study.

Tables Icon

Table 2 – Summary of key technical photometric attributes achieved by “mask and etch” process applied to Iris glass LGP substrates.

Equations (1)

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LDI=[ 1  ( L n+1 +  L n1 )/2 L n ]x 100

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