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Shadow mask

A shadow mask is a thin, perforated metal sheet positioned inside a color cathode-ray tube (CRT) display, featuring thousands to hundreds of thousands of precisely aligned apertures that direct electron beams from three separate red, green, and blue electron guns to strike corresponding phosphor dots on the inner surface of the screen, thereby enabling the accurate reproduction of full-color images by selectively exciting the phosphors to emit red, green, or blue light.^[1] This technology, integral to traditional color CRT televisions and monitors, ensures color purity and prevents crosstalk between beams, with the mask's holes typically arranged in a dot or stripe pattern to match the phosphor triad layout.^[2] Developed as a key innovation for electronic color television, the shadow mask CRT concept originated with Werner Flechsig in Germany in 1938 but was significantly refined by RCA Laboratories engineers, including Alfred Schroeder and Harold B. Law, who demonstrated a practical version in 1950 using a single tube with three guns and a perforated mask to achieve monochrome-compatible color broadcasting.^[3] By 1953, this system formed the basis of the NTSC color television standard approved by the FCC, revolutionizing consumer electronics and becoming the dominant display technology for over four decades until the rise of flat-panel alternatives like LCDs in the late 1990s and early 2000s.^[1] The shadow mask's design allowed for high-resolution color imaging but introduced challenges such as reduced brightness due to the mask absorbing a portion of the electron beams—up to 80% in some configurations—and required precise manufacturing to maintain beam alignment and convergence.^[4] While the classic shadow mask used a flat or slightly curved metal grille with circular holes, variations like the aperture grille (as in Sony's Trinitron) employed vertical slits for improved brightness and resolution, though the shadow mask remained the most widely adopted for standard CRT production due to its simplicity and cost-effectiveness in mass manufacturing.^[5] As of 2025, shadow mask technology is largely obsolete in consumer displays but persists in niche applications such as certain medical imaging systems and legacy equipment, underscoring its historical role in defining analog video display standards.^[2]

Principles of Operation

Basic Mechanism

The shadow mask is a thin, perforated metal sheet positioned immediately behind the phosphor-coated screen in a color cathode-ray tube (CRT), featuring precisely etched apertures that direct electron beams to specific phosphor elements.^[6] This component ensures color purity by preventing crosstalk between beams intended for different primary colors.^[7] Typically placed about 0.5 inches (approximately 12.7 mm) from the inner surface of the faceplate glass, the mask consists of hundreds of thousands of small holes—around 400,000 in a 25-inch tube—with diameters of about 0.012 inches and spacing of roughly 0.029 inches.^[6] The basic operation begins with three separate electron guns, one each for red, green, and blue, arranged in a delta or in-line configuration at the neck of the CRT.^[7] These guns emit focused beams that are simultaneously deflected by external magnetic coils to scan across the shadow mask in a raster pattern.^[8] As the beams converge on the mask, only those electrons passing through aligned apertures reach the phosphor screen; the mask shadows and absorbs stray electrons, ensuring each beam illuminates solely its corresponding phosphor dots or stripes.^[6] The intensity of each beam is modulated by video signals to produce varying shades, with the additive mixing of red, green, and blue light forming the full color spectrum at each pixel position.^[8] At the core of this mechanism is the geometric alignment of the mask apertures with phosphor triads—closely spaced groups of red, green, and blue phosphors arranged in a dot or vertical stripe pattern on the screen.^[7] The guns are angled slightly relative to one another so that their beams approach each aperture from distinct directions, causing them to fan out and strike the appropriate phosphor in the triad beyond the mask; for instance, the red gun's beam passes through a hole to hit only the red phosphor while being blocked from green and blue ones.^[6] This precise shadowing relies on the apparent deflection centers of the beams, maintaining convergence and color separation across the entire display surface.^[6] To visualize the setup, imagine a cross-sectional diagram showing the CRT envelope with the three electron guns at the rear, converging beams passing through a representative mask aperture (a small circular hole), and then separating to excite a triad of phosphor dots on the screen ahead. The mask appears as a grid-like barrier parallel to the screen, with beam paths illustrated as angled lines: the red beam offset to one side of the hole, green straight through the center, and blue to the opposite side, ensuring no overlap in phosphor excitation.^[8]

Alignment and Color Separation

In shadow mask cathode ray tubes (CRTs), color purity is achieved through the precise alignment of the shadow mask's apertures with the phosphor triads on the screen, ensuring that electrons from each of the three electron guns (red, green, and blue) excite only the corresponding phosphor dots without spillover to adjacent colors, thereby maintaining distinct RGB separation.^[9] This separation relies on the mask's metal sheet, positioned approximately 0.5 inches behind the phosphor screen, which absorbs stray electrons and prevents color contamination by blocking unintended beam paths.^[10] Key factors influencing alignment include the convergence of the electron guns, which focuses the three beams to a common point on the screen; the mask-screen spacing, typically fixed during manufacturing to optimize beam focus and purity; and the calibration of the deflection yoke, which magnetically steers the beams across the screen while preserving their alignment.^[11] The positioning of the mask's apertures accounts for the inline or delta arrangement of the guns, with holes offset geometrically to compensate for the angular divergence of the beams: the aperture offset is calculated as \tan([\theta](/page/Theta)) \times d, where \theta is the beam angle relative to the tube axis and d is the mask-screen distance, ensuring each beam passes through the correct hole to reach its phosphor target.^[12] Misconvergence, where the RGB beams fail to overlap perfectly, results in color fringing along edges of images or characters, often due to deflection yoke misalignment or thermal expansion of the mask.^[10] Purity errors, manifesting as mottled or impure colors across the screen, can arise from external magnetic fields that deflect beams away from intended paths or from manufacturing tolerances in mask fabrication, such as variations in hole placement or material stress leading to doming under heat.^[11]^[9] The shadow mask inherently limits the maximum phosphor density and thus the overall resolution of the CRT, as the aperture size—typically 0.1 to 0.3 mm for circular holes or slots—sets the minimum spacing between phosphor elements to avoid beam overlap while maintaining structural integrity of the mask.^[11]^[13] For instance, finer apertures around 0.1 mm enable higher dot pitches (e.g., 0.22–0.28 mm in monitors), supporting resolutions up to approximately 100 dpi, but larger sizes in consumer TVs (0.6–0.9 mm pitch) trade detail for brightness and manufacturability.^[9]

Historical Development

Early Color Television Challenges

In the 1920s and 1940s, early color television efforts centered on mechanical systems, exemplified by John Logie Baird's demonstrations using rotating color filters and Nipkow scanning discs, which achieved the first working color transmission in 1928 but were limited to low resolutions, such as 30 lines, due to mechanical scanning constraints.^[14] These systems also demanded excessive bandwidth for color information, straining transmission infrastructure and resulting in flicker and bulky equipment that hindered practical deployment.^[14] By the 1940s, such mechanical approaches were largely abandoned in favor of electronic methods as television transitioned to all-electronic monochrome standards. Following World War II, electronic color television development prioritized compatibility with the millions of existing black-and-white receivers to ensure widespread adoption without requiring set replacements.^[1] RCA Laboratories led efforts starting in 1946 to create an all-electronic system using the same 6 MHz bandwidth as monochrome broadcasts, incorporating innovations like "mixed highs" for bandwidth efficiency and a "color killer" circuit to prevent interference on black-and-white sets.^[1] This culminated in the National Television System Committee (NTSC) standards adopted by the FCC on December 17, 1953, which encoded color as a subcarrier modulated for hue and saturation while preserving monochrome compatibility.^[1] A central engineering challenge was selecting between single-gun and multiple-gun cathode-ray tube (CRT) designs for color separation. Multiple-gun approaches required three electron beams for red, green, and blue phosphors, complicating convergence and focus across the screen, particularly in larger tubes.^[4] Single-gun alternatives, such as beam-indexing tubes, used vertical phosphor stripes and index signals from UV-emitting strips to synchronize beam modulation with color positions, but suffered from synchronization errors due to phase shifts and signal-processing delays, alongside low overall brightness from inefficient phosphor excitation.^[15] Similarly, the Penetron tube employed a single gun with variable beam voltages to penetrate layered phosphors for different colors, yet encountered low writing speeds from voltage switching, reduced color purity from phosphor filtering, and inherently low brightness due to efficiency losses at higher voltages.^[7] Specific setbacks highlighted these hurdles, including the Columbia Broadcasting System's (CBS) 1951 mechanical field-sequential color system, which rotated filters at 144 fields per second to interleave colors but operated incompatibly with the NTSC's 60-field monochrome standard, rendering it unusable on existing sets.^[16] The FCC initially approved it in 1950 but reversed course by 1953, favoring the compatible NTSC approach amid industry opposition.^[16] Early electronic precursors like the Chromatron tube, developed in the early 1950s by Ernest Lawrence's team using vertical wire grids to deflect a single beam toward phosphor stripes, promised higher brightness by avoiding light-blocking masks but faltered due to precise grid alignment difficulties and manufacturing complexities that limited yields.^[17] These persistent issues in achieving reliable, bright, and compatible color reproduction underscored the need for innovative solutions in the mid-1950s.

Invention and Prototypes

The shadow mask technology for color cathode-ray tubes (CRTs) originated with a 1938 German patent filed by physicist Werner Flechsig, which described a perforated metal sheet to direct electron beams toward corresponding red, green, and blue phosphors on the screen, enabling simultaneous color generation without mechanical filtering. This fixed-mask approach marked a significant departure from earlier color television attempts, such as sequential systems using rotating color filters or wheels that scanned phosphors in time, by allowing three independent electron guns to project RGB beams concurrently for improved stability and compatibility with monochrome signals.^[18] Following World War II, RCA Laboratories licensed Flechsig's patent and pursued refinements in the late 1940s, led by engineer Harold B. Law, who developed patents addressing beam alignment, mask precision, and thermal stability to make the design viable for practical use.^[19] Experimental prototypes emerged between 1948 and 1950, including RCA's first shadow-mask CRT—a 16-inch metal-cone tube demonstrated to the FCC and press in March 1950—which overcame initial alignment issues but revealed challenges like mask doming, where electron bombardment heated the mask by up to 90°C, causing thermal expansion and phosphor misalignment.^[20]^[21] A key milestone came in October 1951, when RCA publicly demonstrated a complete three-gun shadow-mask system integrated with the NTSC color broadcasting standard, achieving monochrome compatibility and sufficient brightness for laboratory viewing on 15- to 16-inch screens, paving the way for further optimization. These prototypes addressed early color television hurdles, such as beam indexing inaccuracies in sequential methods, by relying on precise mask apertures—typically around 200,000 holes—to ensure color separation without moving parts.^[22]

Commercial Adoption

The commercial adoption of shadow mask technology in cathode-ray tube (CRT) televisions began with the market introduction of the RCA CT-100 in 1954, marking the first consumer color TV set utilizing this system. This 15-inch model, priced at $1,000—equivalent to over $10,000 in today's dollars—was produced in limited quantities and targeted the U.S. market, where it aligned with the National Television System Committee (NTSC) color broadcasting standard.^[23]^[24] Key factors enabling this rollout included the Federal Communications Commission's (FCC) approval of the NTSC color standards on December 17, 1953, which provided a compatible framework for broadcasting alongside existing black-and-white transmissions. However, initial sales were modest, with approximately 5,000 units sold in 1954, hampered by the high cost relative to black-and-white sets (typically $200–$300) and the dominance of monochrome programming and receivers in households.^[25]^[24] By the 1960s, adoption expanded globally as European and Japanese manufacturers entered the market, adapting shadow mask CRTs to regional standards like PAL and SECAM. Companies such as Philips in Europe and Sony in Japan began producing color sets, with Sony launching its first color televisions using an early Chromatron variant in 1964 before shifting to Trinitron technology. In the U.S., color TV penetration in households reached about 10% by the end of 1965, driven by increasing network programming and falling prices.^[26]^[27] Early improvements during this period focused on enhancing usability and performance, including the availability of larger screens up to 25 inches by 1967, which broadened appeal for home entertainment. Additionally, better convergence—ensuring precise alignment of red, green, and blue electron beams—was achieved through electronic adjustments in receiver circuits, reducing the need for manual tweaks and improving picture quality over initial models.^[28]^[29]

Manufacturing and Design

Construction Materials

The shadow mask in cathode-ray tube (CRT) displays is primarily constructed from Invar, a nickel-iron alloy valued for its exceptionally low coefficient of thermal expansion, which prevents distortion and misalignment due to heating from electron beam absorption.^[30] This material allows the mask to maintain structural integrity under operational temperatures, absorbing up to 80% of the incoming electron energy without significant warping.^[31] The sheet thickness typically ranges from 0.1 to 0.3 mm, balancing mechanical strength with the need for precise electron passage.^[32] The mask features an array of finely etched apertures, generally circular or rectangular in shape with diameters of 0.15 to 0.4 mm, arranged in either a hexagonal pattern for traditional triad phosphor layouts or linear stripes for slot-type designs. These apertures are photochemically machined to ensure exact correspondence with the underlying phosphor dots or stripes, facilitating color separation by directing electron beams to specific luminescent areas. A supporting frame, typically made of steel or aluminum, secures the mask edges and maintains its taut, curved profile within the CRT envelope, preventing sagging or vibration during use.^[33] The adjacent phosphor screen employs specific compositions for color emission, including yttrium oxysulfide doped with europium (Y₂O₂S:Eu) for red, zinc sulfide doped with copper (ZnS:Cu, often with aluminum co-doping) for green, and zinc sulfide doped with silver (ZnS:Ag) for blue.^[34] The complete assembly resides in a vacuum-sealed glass envelope maintaining an internal pressure of approximately 10⁻⁶ torr to enable unimpeded electron travel, with the mask engineered to endure this high vacuum alongside prolonged electron bombardment that generates localized heating and potential ionization.^[35] This durability ensures long-term alignment of electron beams with phosphors, critical for consistent color reproduction.^[31]

Production Methods

The production of shadow masks for cathode ray tubes (CRTs) primarily involves a photo-lithographic etching process applied to a thin Invar sheet, selected for its low thermal expansion properties. The sheet, typically 0.15 to 0.30 mm thick, is first cleaned and coated with a photosensitive resist on both sides. A high-resolution photographic master, defining the precise pattern of apertures, is aligned and exposed to ultraviolet light, hardening the resist in the desired areas while leaving the metal surfaces corresponding to the holes unprotected. After development to remove the unexposed resist, the sheet is immersed in or sprayed with a ferric chloride-based etchant solution at controlled temperatures (around 40–50°C) to dissolve the exposed Invar selectively from both sides, forming tapered holes with smooth walls. This isotropic wet etching process, often taking several hours, yields over 200,000 apertures in a standard 20-inch (51 cm) mask, with hole diameters ranging from 0.2 to 0.4 mm depending on screen resolution requirements.^[36] Following etching, the mask undergoes post-processing, including resist stripping via chemical solvents or plasma ashing, and surface cleaning to remove etchant residues. The etched Invar sheet is then deep-drawn into a curved dome shape matching the CRT's spherical or cylindrical geometry, typically using hydraulic presses to achieve the precise radius of curvature. Edges are trimmed, and the mask is welded to a rigid steel frame with tensioning springs to maintain flatness under thermal stress. Assembly into the CRT proceeds with mounting the framed mask inside the glass envelope, aligned precisely to the phosphor screen using fiducial markers. The phosphor screen, located on the inner surface of the faceplate, is prepared separately via cataphoretic settling (electrophoretic deposition), where suspensions of red, green, and blue phosphors in an aqueous medium are sequentially applied under an electric field, causing particles to migrate and adhere uniformly to form triads of dots or stripes aligned with the mask holes. Electron guns are then mounted in the neck of the funnel section, with deflection yokes and convergence adjustments calibrated for mask alignment. The faceplate, funnel, and stem are joined using low-melting-point frit glass seals, and the assembly is baked in a vacuum furnace at 400–450°C to outgas impurities and achieve a high vacuum (below 10^{-7} torr), followed by tip-off sealing of the exhaust tube.^[4]^[37] Quality control throughout production emphasizes precision to ensure color purity and prevent misconvergence. Optical inspection systems, often using automated laser scanning or machine vision, verify hole uniformity, aperture size variation (typically held to ±5% tolerance), and overall pattern fidelity across the mask surface, detecting defects like bridging or under-etching that could cause phosphor misregistration. Thermal cycling tests simulate operational heating by subjecting sample masks to repeated temperature excursions from 20°C to 80°C in environmental chambers, measuring dimensional stability to confirm the Invar alloy's linear expansion coefficient remains below 5 ppm/°C, mitigating "doming" distortions where mask curvature changes due to uneven heating from electron beam scanning. Failed units are rejected or reworked, with yield rates improved through process controls like etchant regeneration and real-time monitoring.^[38]^[39] In the 1970s, as color television demand surged, major manufacturers like RCA and Sony scaled shadow mask CRT production to millions of units annually through automation of etching lines, robotic framing, and inline inspection, reducing per-unit costs from over $50 in the early decade to under $20 by the late 1970s and enabling global output of 20–25 million color sets per year.^[4]^[40]

Variations and Improvements

Aperture Grille Comparison

The aperture grille, pioneered in Sony's Trinitron color television system developed in 1968, serves as a key variation to the conventional shadow mask used in cathode-ray tubes (CRTs) for color separation. While the standard shadow mask relies on a perforated metal sheet with discrete holes—typically achieving 20-30% electron transmission—the aperture grille employs an array of fine vertical wires under tension, forming elongated slot-like openings that permit greater beam passage and reduce obstructive material. This structural shift allows the Trinitron design to transmit approximately 50% more light than traditional shadow masks, enabling higher brightness levels without increasing power consumption.^[41]^[42] Fundamental differences lie in their geometries and operational requirements. The shadow mask's circular or oval holes align with individual phosphor triads, but this dense patterning can induce moiré interference patterns from the interaction between holes, phosphors, and scan lines. In contrast, the aperture grille's vertical slots span across phosphor stripes, minimizing such artifacts and supporting sharper vertical resolution. To function effectively, the grille necessitates an inline electron gun arrangement—often a single gun with three inline cathodes—ensuring the red, green, and blue beams converge precisely through the slots without crosstalk.^[41] These design choices yield notable trade-offs in performance. The aperture grille excels in focus uniformity and luminance, contributing to the Trinitron's reputation for vibrant, high-contrast images in demanding viewing environments. However, the tensioned wires offer less mechanical stability than the rigid shadow mask, rendering larger-screen implementations more vulnerable to geometric distortions like pincushion or convergence errors under thermal expansion or external magnetic influences. Sony secured patents for this technology and launched the Trinitron commercially in Japan in October 1968, followed by U.S. introduction in May 1969, positioning it as a premium feature in high-end CRT televisions through the 1990s.^[43]

Later Enhancements

In the 1990s, the tension mask emerged as a significant refinement to shadow mask technology, utilizing a flat Invar sheet— an iron-nickel alloy with low thermal expansion—stretched under tension within the CRT frame.^[44] This design minimized thermal doming, where heat from electron beam impacts caused mask distortion and color impurities, allowing for thinner masks (50–80 μm thick) that maintained structural integrity under high temperatures.^[44] By reducing these distortions, tension masks enabled the production of larger flat-panel CRTs, reaching up to 40 inches diagonally while preserving uniform electron beam landing and image quality.^[44] Slot mask designs further enhanced resolution by replacing circular apertures with rectangular slits, which improved electron beam transmission efficiency and reduced the moiré effect from phosphor-dot interference.^[45] These vertical slits, typically spaced with narrow bridges, allowed for finer pitch structures; for instance, high-quality models in the mid-1990s achieved a 0.25 mm stripe pitch, supporting sharper images suitable for consumer televisions and monitors.^[9] This configuration increased brightness and contrast without compromising color purity, making slot masks prevalent in post-1990s CRT production.^[45] Material advancements included metal coatings on the shadow mask surface to augment heat dissipation and capacity, addressing the issue of localized heating that led to expansion and misconvergence.^[46] These coatings, applied to traditional steel or Invar bases, transferred heat more effectively to the frame, stabilizing the mask during prolonged operation and enabling higher beam currents for brighter displays. Complementing this, dynamic convergence circuits were integrated to correct beam misalignment errors across the screen periphery.^[47] These circuits employed polynomial corrections—combining analog coarse adjustments with digital fine-tuning via PROMs and D/A converters—to achieve misconvergence below 0.05 mm, ensuring precise color registration even in larger tubes.^[47] These enhancements collectively facilitated the market penetration of affordable large-screen CRTs, such as 32-inch models that became widely available by 2000, driving consumer adoption through improved performance at competitive prices.^[48] By mitigating brightness limitations inherent to earlier shadow masks, later designs supported peak luminances approaching 500 cd/m² in optimized configurations, extending the technology's viability for home entertainment into the early 21st century.

Advantages, Limitations, and Legacy

Performance Benefits

Shadow mask CRTs deliver high color accuracy due to the precise separation of red, green, and blue electron beams by the mask's apertures, enabling well-calibrated displays to reproduce up to 100% of the NTSC color gamut.^[49] This RGB isolation minimizes color contamination, ensuring faithful representation of broadcast signals and supporting vibrant, true-to-life imagery in consumer televisions.^[49] The phosphor excitation process in shadow mask CRTs facilitates peak luminance levels exceeding 400 cd/m², providing bright images suitable for various viewing conditions.^[50] Additionally, the technology achieves deep blacks in dark environments through the inherent ability of CRTs to turn off pixels completely, enhancing contrast ratios without backlight interference.^[51] Shadow mask CRTs exhibit proven durability, with average operational lifespans surpassing 20,000 hours under typical use. Phosphor degradation occurs gradually and can often be mitigated through usage patterns. Economically, shadow mask CRTs proved highly cost-effective for mass production during the 1980s and 1990s, leveraging standardized manufacturing processes to capture over 90% of the color television market by 1990.^[4] This dominance stemmed from efficient scaling of components like the mask and electron guns, making high-quality color displays accessible to consumers worldwide.^[4]

Technical Drawbacks

One major technical drawback of shadow mask technology is the significant loss of electron beam energy, as the mask absorbs approximately 80% of the electrons, allowing only 20-30% to pass through the apertures and excite the phosphors.^[52] This inefficiency necessitates higher power input to maintain brightness levels, with 30-inch CRT televisions typically consuming 150-200 watts during operation.^[53] The doming effect, caused by thermal expansion of the mask under electron beam heat, leads to shifts in aperture positions relative to the phosphor dots, resulting in focus degradation and color misregistration.^[54] Although materials like Invar help mitigate this issue through low thermal expansion coefficients, displacements of up to 0.5 mm can still occur, requiring design tolerances that are not fully eliminated.^[55] Shadow mask CRTs are inherently bulky and heavy due to their curved glass envelope and internal components, which prevent flat-panel designs and contribute to overall set weights of 50-100 kg for large sizes like 30-inch models.^[56] Resolution is constrained by the physical size of mask apertures and phosphor dot pitch, typically around 0.5 mm in consumer CRTs, limiting pixel density compared to modern LCDs that achieve pitches as fine as 0.1 mm.^[57]

Decline and Replacement

The emergence of flat-panel display technologies, particularly liquid crystal displays (LCDs) and plasma displays, in the 1990s marked the beginning of the shadow mask CRT's decline, as these alternatives offered slimmer profiles and greater scalability for larger screens. Commercial LCD televisions appeared in the late 1990s, with shipments growing rapidly from under 1 million units in 2000 to over 50 million by 2007, gradually eroding CRT dominance.^[58] By 2008, LCD TV shipments surpassed CRTs for the first time globally, capturing 47% of the market compared to CRT's 46% in the fourth quarter.^[59] CRT market share continued to plummet, falling from 84% in 2005 to 57% by 2009 and below 10% by 2012, when shipments totaled just 15.5 million units out of 238.5 million total TVs worldwide.^[60]^[61]^[62] Key drivers of this shift included the physical advantages of flat-panel technologies, such as their thinness and reduced weight—LCDs measured just a few inches deep versus the bulky depth of CRTs exceeding two feet for large models—making them easier to manufacture, ship, and install in modern homes.^[63] Flat-panels also consumed significantly less power, typically 45-100 watts for a 19-32 inch LCD compared to 100-200 watts for equivalent CRTs, lowering operational costs and energy demands.^[64] Additionally, the adoption of digital interfaces like HDMI enabled seamless integration with high-definition content and home theater systems, contrasting with CRTs' reliance on analog signals that limited resolution and compatibility.^[65] Environmental regulations further accelerated the phase-out; the European Union's RoHS Directive, effective from 2006, restricted hazardous substances like lead used in CRT glass, increasing production costs and prompting manufacturers to exit the market by 2007 in compliant regions.^[66] Major CRT production lines shut down progressively through the early 2010s, with the last significant consumer TV assembly occurring around 2015 by India's Videocon using refurbished components, after global giants like Samsung ceased operations in 2012.^[67] While consumer applications vanished, legacy CRTs persist in niche medical imaging setups, providing reliable grayscale accuracy for diagnostic equipment in specialized clinics.^[68] The shadow mask technology underpinned color television for over five decades, enabling the production of more than 1 billion CRT devices worldwide and establishing foundational display standards.^[69] Its phosphor deposition techniques directly influenced modern LED displays, where similar rare-earth phosphors convert blue light to white, powering backlights in billions of contemporary screens.^[70]

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The ferric chloride etching of aluminum-killed(AK) steel and Invar alloy was studied. The effect of process parameters(i.e., etchant temperature, ...Missing: CRT photo- lithographic
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[PDF] manufacture of color picture tubes
4. Tapering the holes in a shadow mask reduces electron scatter, increases beam intensity, and achieves increased light output as well as better contrast and ...
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(PDF) Analysis of the Machining Depth over Time in Wet Etching for ...
Shadow mask is an important element for enhancing the pixels of the display. Therefore, Wet etching is an important machining technique because it is economical ...
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With this construction, when the temperature of the shadow mask was increased to the mean operating temperature of the color picture tube which is about 30C ...<|separator|>
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Oct 28, 1973 · According to industry statistics, between 20 million and 25 million color TV sets will be sold throughout the world this year. At an ayerage ...
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Sony calls the mask an aperture grille. The phosphor stripes are very narrow compared to the beams. Each beam spreads across two slots in the grille. But ...
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An eventful 1961 drew to a close on December 16, when Sony concluded a contract with Paramount Pictures to provide technical assistance in the production of a ...Missing: patent | Show results with:patent
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The present invention relates to a flat tension mask type CRT which improves structures of a shadow mask and a panel, herein the shadow mask has a thickness ...Missing: development 1990s Invar sheet
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Making shadow mask with slit-shaped apertures for CRT
Each of the slits of the shadow mask prepared in this manner has larger length and width than the dot patterns 14 and 16 of the first and second negative films, ...
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The present invention forms a metal coating layer with a large heat capacity on the surface of the shadow mask to increase the heat capacity of the shadow mask ...
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The most commonly used color CRT tubes are the shadow-mask type, in which a ... This justifies and explains the relatively accurate color reproductions obtained.
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AMLCD displays provide brighter images than CRT displays in raster mode, with backlights producing over 1000 cd/m2 of luminance compared to around 700 cd/m2 for ...
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CRT ARCHITECTURES - SPIE Digital Library
A shadow mask would be immune to vi- bration of the same intensity. An example is an ultrasound cart being bumped and disturbing the color purity until the ...
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Heating of the shadow mask caused by the CRT's electron beams incident thereon gives rise to heating and thermal expansion of the shadow mask metal holders.
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Apr 30, 1993 · The final FTM mask/panel assembly has a mask-to-screen spacing variation of .004 inches compared to a conventional assembly variation of up to .<|separator|>
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Jul 4, 2022 · 30" widescreen standard-definition CRT by Philips. Originally manufactured in Mexico. It is lovely gem of a TV ... Weight: 123 lbs (55.8 kg).
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In most CRTs you measure dot pitch as the distance between holes in the shadow mask. ... A good dot pitch is typically between 0.20 and 0.35 millimeters.
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Feb 22, 2008 · CRT still raked in a 46 per cent share during the period, but the figure is far removed from the 77 per cent share the technology enjoyed in ...<|control11|><|separator|>
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Between 2005 and 2009, CRTs will go from an 84 per cent market share to 57 per cent. They will account for less than half of all sales by 2010. Although there ...Missing: timeline | Show results with:timeline
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Apr 1, 2013 · Television shipments in 2012 totaled 238.5 million units, down 6.3% from 254.6 million in 2011, according to a report Monday by IHS iSuppli.
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The optical properties of the glass used on the screen affect color reproduction and purity in color CRTs. ... shadow mask of a color CRT. The velocity of the ...Shadow mask · Electron gun · Oscilloscope · Sony PVM-4300
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Nov 29, 2019 · Almost twenty years ago, LCD screens began to replace traditional CRT monitors in diagnostic imaging. Their thinner size, reduced energy ...
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almost all of ...
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Close to the phosphor screen is a shadow mask, a sheet steel shield ... The generation of white light by the UV LED/phosphor technology has one very ...