Commission International Eclairage Research Articles

Rational design and coloration mechanism of soluble intrinsic black polyimide with high comprehensive performance for black flexible copper clad laminates

With the development of flexible printed circuit boards (FPCBs) and photoelectric devices, the demand for black polyimide (BPI) is increasing, but the existing BPIs have some problems, such as poor electrical properties, mechanical performance, masking ability and solubility. To solve these problems, a novel diamine monomer (TPCPOHPDA) containing tetraphenylcyclopentadienone (TPCP) grafted with hydroxyl groups and benzene rings was customized, and then TPCPOHPDA was polymerized with 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) to obtain polyimide (TPCPOHPPI). TPCP had a broad UV–visible light absorption range (250–600 nm). Appending benzene rings and auxochrome (hydroxyl groups) on the TPCP skeleton extended the conjugated π-electron system and enhanced the mobility of electrons in the large π bonds, respectively. These structural modifications further extended its light absorption range, and the resulting TPCPOHPPI was dark black with a cutoff wavelength (λcut) of 680 nm and Commission International Eclairage (CIE) lab color parameter L* of 0.7. Simulation calculations indicated that the visible-light absorption that caused the black appearance of TPCPOHPPI was mainly due to the electron transition from HOMO to LUMO occurring within the TPCP-containing diamine moieties, in which the charge mainly transferred from the aryl moieties in positions 2 and 5 to the central cyclopentadienone core. Further investigation showed that TPCPOHPPI had excellent thermal, electrical and mechanical performances and high solubility. The TPCPOHPPI-based two-layer black flexible copper clad laminate (2L-FCCL) possessed good dip soldering resistance and peeling strength. This work provides a new idea for the design and synthesis of soluble intrinsic black polyimide with excellent comprehensive performance.

Rational design of high-performance soluble intrinsic black polyimide with full absorption of visible light

With the rapid development of photoelectric devices, the demand for black polyimide (BPI) with excellent masking ability is growing, but existing BPI doped with black substrates has serious insulation and mechanical performance deficiencies. To solve the problem, the intrinsic BPI with excellent comprehensive performance is highly desirable. In this work, tetraphenylcyclopentadienone (TPCP) was chosen as a chromophore, a novel diamine (TPCPtPPDA) containing TPCP grafted with biphenyl groups was synthesized, and TPCPtPPDA was then polymerized with 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) to obtain a black polyimide (TPCPtPPPI). The TPCPtPPPI showed full absorption of visible light with cutoff wavelength (λcut) high to 713 nm and Commission International Eclairage (CIE) lab color parameter L* of 0.82. By calculating the frontier molecular orbitals and the nature of electron transitions, the excellent light absorption property was attributed to the electron transition from HOMO to LUMO occurring in the diamine moieties, with the charge transfer mainly from the terphenyl moieties in 2 and 5 positions to the central cyclopentadienone core. Meanwhile, TPCPtPPPI also had excellent thermal, electrical and mechanical performances and solubility by introduction of rigid non-planar propeller-shaped structure. This work provides a promising strategy for constructing high-performance soluble intrinsic BPI and related polymers with full absorption of visible light.

Yield estimation of citrus fruit using rapid image processing in natural background

Yield estimation can provide critical information for high-value crop growers. It helps them to plan and coordinate the logistics of harvesting operations. Most existing yield estimation techniques are based on manual sampling and statistical approaches, which are complex, labor-intensive, and time-consuming. In recent years, advances in image processing and the ubiquitous use of autonomous platforms, such as unmanned aerial platforms, have provided an opportunity for faster and more accurate yield estimation techniques for different crops. A new rapid, efficient, and accurate image processing algorithm was proposed in this study. The image segmentation technique was able to separate mature citrus trees and natural background in CIE (Commission International Eclairage) L*a*b* (i.e., Lab) color space. The effect of camera distance to object, affected resolution, and detection accuracy were evaluated and discussed. The results showed that the distance between 1.524 meters (5 feet) and 2.134 meters (7 feet) could provide high detection accuracy. The number of correctly counted fruit reached 91.69% at the average processing time of 1.1 s per picture for 132 pictures. A correlation coefficient (R2) of 0.98 was obtained between the citrus counting algorithm and counting performed through human observation of 66 sample trees. The comparative analysis of the proposed method showed a higher accuracy rate and robustness compared to other similar studies.

Improvement of properties of smart ink via chitin nanofiber and application as freshness indicator

Chitin nanofiber decorated with both cationic (NH3+) and anionic (COO−) is fabricated by partial deacetylation and TEMPO-oxidation (TEMPO/NaClO2/NaClO) system. As-prepared zwitterionic chitin nanofiber has particle size around 395 nm and excellent dispersibility. It could synergize with chitosan to immobilize anthocyanin for manufacturing smart ink, which is proved to be mainly stabilized by hydrogen bond. Chitin nanofiber could improve the rheology properties including yield stress and shearing viscosity of the ink, and result in excellent printability with rub resistance and tape fastness being up to 97.8 % and 98.9 % respectively. The screen-printed label (based on smart ink) displays different colors and shows certain color change trend under different pH conditions. Analysis of the volatile basic nitrogen, CIE Lab (Commission International Eclairage color model) and pH demonstrates the effective indicating properties of the label for fish freshness level. The application on fish proves that this screen-printed label could be an easy, green way to determine the meat freshness.

Fabric defect detection using saliency of multi‐scale local steering kernel

Fabric defect detection (FDD) plays an important role in the quality control in textile industry. In this study, the authors propose an efficient FDD method by using the saliency analysis of multi-scale local steering kernel (LSK). In the proposed method, a given RGB fabric image is first converted into the Commission International Eclairage (CIE) L*a*b colour space and then the LSK in each colour channel is computed by the singular value decomposition and the centre surrounding definition. Next, the matrix cosine similarity is employed to measure the similarity between different LSK features for generating the desired defective maps. Finally, a multi-scale averaging fusion scheme is applied to integrate the obtained defective maps at different scales for the final defective map. The experimental results indicate that the proposed method achieves the state-of-the-art performance on FDD compared to the other competitors.

Preparation and Properties of Inherently Black Polyimide Films with Extremely Low Coefficients of Thermal Expansion and Potential Applications for Black Flexible Copper Clad Laminates

In the current work, a series of black polyimide (PI) films with excellent thermal and dimensional stability at elevated temperatures were successfully developed. For this purpose, two aromatic diamines including 4,4′-iminodianline (NDA) and 2-(4-aminophenyl)-5- aminobenzimidazole (APBI) were copolymerized with pyromellitic dianhydride (PMDA) to afford PIs containing imino groups (–NH–) in the molecular structures. The referenced PI film, PI-ref, was simultaneously prepared from PMDA and 4,4′-oxydianiline (ODA). The introduction of imino groups endowed the PI films with excellent blackness and opaqueness with the optical transmittance lower than 2% at the wavelength of 600 nm at a thickness of 25 μm and lightness (L*) below 10 for the CIE (Commission International Eclairage) Lab optical parameters. Meanwhile, the introduction of rigid benzimidazole units apparently improved the thermal and dimensional stability of the PI films. The PI-d film based on PMDA and mixed diamines (NDA:APBI = 70:30, molar ratio) showed a glass transition temperature (Tg) of 445.5 °C and a coefficient of thermal expansion (CTE) of 8.9 × 10−6/K in the temperature range of 50 to 250 °C, respectively. It is obviously superior to those of the PI-a (PMDA-NDA, Tg = 431.6 °C; CTE = 18.8 × 10−6/K) and PI-ref (PMDA-ODA, Tg = 418.8 °C; CTE: 29.5 × 10−6/K) films.

The Changes in Color, Soluble Sugars, Organic Acids, Anthocyanins and Aroma Components in "Starkrimson" during the Ripening Period in China.

“Starkrimson” is a traditional apple cultivar that was developed a long time ago and was widely cultivated in the arid region of the northern Wei River of China. However, little information regarding the quality characteristics of “Starkrimson” fruit has been reported in this area. To elucidate these characteristics, the color, soluble sugars, organic acids, anthocyanins and aroma components were measured during the ripening period through the use of high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). The results indicated that the changes in anthocyanin contents took place later than the changes in the Commission International Eclairage (CIE) parameters. Meanwhile, cyanidin 3-galactoside (cy3-gal), fructose, sucrose, glucose and malic acid were the primary organic compounds, and 1-butanol-2-methyl-acetate, 2-hexenal and 1-hexanol were the most abundant aroma components in the skin. Furthermore, rapidly changing soluble sugars and organic acid synchronization took place in the early ripening period, while rapidly changing aroma components occurred later, on the basis of fresh weight. This result suggested that the production of aroma components might be a useful index of apple maturity.

Phosphorescent hybrid organic-inorganic light emitting devices with solution-processed small molecule emissive layers

We report efficient phosphorescent hybrid organic-inorganic light emitting devices using poly(ethylenimine) as electron-injection layer and interfacial modifier for metal oxides and solution-processed small molecule emissive layers. As a first step, the hole transport layers with various HOMO levels and the hole mobility values including TAPC, TCTA and mCP are evaluated. The results indicate that devices using a TAPC layer show the best luminance and power efficiencies. Subsequently, the optimum phosphor concentration is determined to be ca. 5%. Enlarged efficiency roll-off with increasing current density is observed in devices using the phosphor concentration above the optimum value. We also investigate the morphologies of films having different phosphor concentrations on the top of bare or PEIE-covered glass substrates, which is closely related to device performance. All the films have the RMS values of ca. 1 nm, indicating high-quality solution processed small molecule films. The blue, yellow and red devices show the maximum external quantum efficiencies of 17.3%, 10.7% and 7.3%, respectively. These efficiencies are 17.0%, 10.6% and 5.8% at 1000 cd·m-2, only showing a small roll-off, which can be attributed to alleviated triplet-triplet and triplet-polaron interactions in a broad carrier recombination zone due to using the mixed hole-transport and electron-transport materials as the co-hosts. In addition, these devices exhibit the respective Commission International Eclairage (CIE) coordinates of (0.16, 0.36), (0.50, 0.49) and (0.66, 0.32), which almost traverse the whole visible light region. Furthermore, the hybrid two-colored white devices show a luminance efficiency of 31 cd·A-1, power efficiency of 14.8 lm·W-1 at 1000 cd·m-2 and the operating current-insensitive CIE coordinates of (0.32, 0.42). The efficiencies represent the significant improvement over the previously reported values, which can be attributed to high-quality small molecule films on PEIE, and in particular to the unique properties of small molecule host materials such as balanced carrier transport and high triplet energy. Further efforts including selection of high-mobility electron transport host material and phosphors with high luminescence quantum yield are made to increase the efficiency and reliability of hybrid organic-inorganic light emitting device.

Photoluminescence properties of Ce and Eu co-doped YVO4 crystals

High-quality Ce3+ and Eu3+ co-doped YVO4 crystals were grown by the Czochralski method in a medium frequency induction furnace. The X-ray Diffraction (XRD) patterns revealed that they were tetragonal crystals and no changes in the crystalline phases were observed after doping. The luminescence of YVO4: Ce3+ and YVO4: Ce3+/Eu3+ crystals were measured at room temperature. Both YVO4: Ce3+ and YVO4: Ce3+/Eu3+ crystals can be excited at 325nm: the former emitted blue light while the latter emitted red light. This phenomenon can be explained by the V–O charge transfer transitions. Particularly, the mechanisms of Photoluminescence (PL) and Photoluminescence Excitation (PLE) of YVO4: Ce3+ and YVO4: Ce3+/Eu3+ crystals have been thoroughly investigated in this work. The Commission International Eclairage (CIE) coordinates were also calculated for these crystals. The calculated CIE coordinates indicated that the YVO4: Ce3+/Eu3+ crystal prepared in this work, when excited at 397nm, could be a promising material for white light-emitting diodes.