Light Transmittance Testing Services for Advanced Display Materials

Light transmittance testing for new display materials is a critical step in verifying the optical performance of OLED, LCD, quantum dot, and flexible display components throughout the development and manufacturing cycle. Accredited third-party laboratories provide precise transmittance, haze, and spectral measurements using UV-Vis spectrophotometry and integrating sphere techniques in accordance with ASTM, ISO, IEC, and GB standards. This article outlines the testing scope, applicable methods, sample requirements, and typical applications of professional transmittance determination services for next-generation display materials.

Technical Overview

Transmittance, defined as the ratio of luminous flux passing through a material to the incident luminous flux, is one of the most fundamental optical parameters in display engineering. For modern display materials, transmittance directly determines brightness, energy efficiency, contrast, and visual clarity of the final panel. Even a one-percent deviation in the transmittance of an optical film or functional layer can significantly affect backlight power consumption or OLED luminance efficiency at the module level.

New display materials, including organic light-emitting materials, quantum dot films, polarizers, diffuser sheets, brightness enhancement films, transparent conductive films, ultra-thin glass, and colorless polyimide substrates, all require rigorous optical characterization. Professional transmittance determination services measure not only total luminous transmittance but also haze, spectral distribution, uniformity, and color-related optical indices, providing material suppliers, panel manufacturers, and R&D teams with reliable data for product qualification, incoming inspection, and process optimization.

Testing is typically performed in ISO/IEC 17025 accredited third-party laboratories using calibrated hazemeters and UV-Vis spectrophotometers equipped with integrating spheres, ensuring traceable, repeatable, and internationally recognized results.

Testing Samples

OLED and Emerging Emissive Materials

Organic functional materials used in OLED, QLED, and micro-LED devices, including hole injection layers, hole transport layers, emission layers, electron transport layers, and thin-film encapsulation coatings, can be tested as coated glass substrates or free-standing films to evaluate optical losses across the visible spectrum.

Liquid Crystal Display Materials

Liquid crystal cells, alignment layers, polarizers, compensation films, and retardation films are measured to verify transmittance uniformity, extinction performance, and spectral consistency required for high-resolution LCD panels.

Optical Films and Backlight Components

Diffuser films, brightness enhancement films (BEF), reflective sheets, and quantum dot enhancement films (QDEF) are characterized for total transmittance, haze, and angular scattering behavior, which govern the light management efficiency of backlight units.

Transparent Conductive Films and Cover Materials

ITO-coated glass and film, metal mesh conductive layers, Ag nanowire films, cover glass, chemically strengthened glass, and sapphire windows are tested to balance electrical conductivity with maximum optical clarity.

Flexible Substrates and Optical Adhesives

Colorless polyimide (CPI) films, ultra-thin flexible glass, optically clear adhesives (OCA), and pressure-sensitive adhesive films are evaluated for transmittance, haze, and yellowness index, which are key acceptance criteria for foldable and rollable display architectures.

Testing Items

Comprehensive transmittance determination services for display materials typically cover the following optical parameters:

• Total luminous transmittance (Tt) measured under standard illuminants (D65, C, or A) with 2° or 10° standard observers
• Haze (diffuse transmittance ratio) for evaluating light-scattering behavior of films and diffusers
• Spectral transmittance scanning across the 200–800 nm or 380–780 nm wavelength range
• Regular (parallel light) transmittance for assessing image clarity and transparency
• Transmittance uniformity mapping across the sample surface
• Yellowness index and whiteness index calculated from spectral data
• Chromaticity coordinates (CIE x, y; L*a*b*) of transmitted light
• Ultraviolet and infrared transmittance characterization for cutoff and blocking performance
• Solar transmittance determination for automotive and outdoor display applications

Testing Methods

Transmittance testing is performed according to internationally recognized standards, ensuring comparability and mutual acceptance of results across global supply chains:

• ASTM D1003 — Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics, covering both hazemeter (Method A) and spectrophotometer (Method B) procedures
• ISO 13468-1 / ISO 13468-2 — Determination of the total luminous transmittance of transparent materials using single-beam and double-beam instruments, respectively
• ISO 14782 — Determination of the luminous transmittance of transparent materials, applicable to haze measurement
• GB/T 2410 — Chinese national standard for transmittance and haze of transparent plastics, widely referenced in domestic supply chains
• ASTM E903 — Solar absorptance, reflectance, and transmittance of materials using integrating spheres
• JIS K 7361-1 and JIS K 7136 — Japanese industrial standards equivalent to ISO transmittance and haze methods

In a typical hazemeter procedure, the sample is illuminated with a standardized light source, and four successive readings are taken to separate total transmittance from wide-angle scattered light, yielding both Tt and haze values. In the spectrophotometric approach, a wavelength scan is performed with an integrating sphere detector, and luminous transmittance is computed by weighting the spectral curve with the selected illuminant and observer functions. All specimens are conditioned in a controlled environment, commonly 23°C and 50% relative humidity, prior to measurement to eliminate moisture-induced deviations. Test reports document the instrument configuration, standard illuminant, specimen thickness, measurement geometry, and individual measurement values with repeatability data.

Applications

Transmittance determination services support every stage of the display industry value chain:

• New material R&D and formulation screening for OLED, quantum dot, and liquid crystal developers
• Supplier qualification and incoming material inspection for panel manufacturers
• Quality control and lot release testing for optical film producers
• Failure analysis and comparative benchmarking of competing materials
• Verification of optical performance for automotive displays, avionics, and outdoor signage
• Component evaluation for AR/VR optical systems, waveguides, and near-eye display modules
• Regulatory and customer documentation requiring traceable third-party test data

By outsourcing transmittance measurements to accredited laboratories, manufacturers gain access to high-precision instrumentation, validated procedures, and internationally accepted test reports without capital investment, while ensuring that optical data submitted to customers meets the most stringent audit requirements.

FAQ

What is the difference between transmittance and haze?

Transmittance quantifies the total amount of visible light passing through a specimen, expressed as a percentage of incident light, whereas haze measures the portion of transmitted light that is scattered at angles greater than 2.5 degrees. A material can exhibit high transmittance yet significant haze, which is desirable for diffuser films but unacceptable for cover glass or OCA layers.

What sample sizes and forms can be tested?

Most laboratories accept specimens of approximately 50 mm × 50 mm or larger for hazemeter measurements, and smaller coupons for spectrophotometer beam apertures. Rigid sheets, coated glass, free-standing films, and flexible substrates can all be accommodated using appropriate film holders. It is recommended to submit samples free of scratches, fingerprints, and dust, as surface contamination strongly affects haze results.

Which standard should be selected for my material?

ASTM D1003 and ISO 13468 are the most widely cited methods for luminous transmittance, while GB/T 2410 is commonly required in the Chinese market. The choice depends on customer specifications, end-market requirements, and regional conventions; testing laboratories can advise on the most suitable method and illuminant for a given application.

How thick can a sample be?

Standard methods are optimized for transparent specimens typically below 10 mm in thickness. Thicker or slightly translucent samples may require modified geometries or alternative approaches, which should be discussed with the laboratory in advance.

What is the typical turnaround time?

Routine transmittance and haze measurements are usually completed within three to five working days after sample receipt, while projects involving spectral scanning, uniformity mapping, or custom illuminant calculations may require additional time. Expedited services are often available upon request.

Are the test results internationally recognized?

When testing is performed by ISO/IEC 17025 accredited third-party laboratories using calibrated instruments and standardized procedures, the resulting reports are recognized by global panel manufacturers, brand customers, and certification bodies, supporting seamless material approval across borders.