新穎性光可交聯樹脂在黑色矩陣之運用:合成、製備、與動力學研究

Abstract

在液晶顯示器產業中，黑色矩陣是彩色濾光片上的一個重要的遮光元件。本研究主要是開發新型的碳黑光阻，其用途是可以使用微影製程來製備高遮光性之黑色矩陣。碳黑光阻包含碳黑、碳黑分散劑、光可交聯樹酯、黏著促進劑、以及光起始劑。本論文分兩部分來探討：一、在碳黑光阻的成分中，其合成以及功能探討。二、光聚合動力學以及穩定自由基聚合動力學探討。 在第一部份中，為了要在溶劑單甲基醚丙二醇醋酸酯(PGMEA)中製備出高濃度且穩定懸浮之碳黑分散液(碳黑含量佔總分散液重量的10%)，首先我們使用分散劑來對碳黑進行表面處理。我們分別使用三種不同的碳黑分散劑:一種商業化的分散劑以及兩種新合成的分散劑。藉由分散劑的氨基與碳黑表面的酸基所產生的作用力，碳黑可以有效的吸附於碳黑表面上。另外，分散劑擁有適當鏈長可以提供碳黑良好的立體穩定性。此外，我們也有探討分散劑的含量與結構對於碳黑的穩定性以及遮光性質的影響。在這些碳黑分散劑中，其中一種分散劑含有methacrylate 官能基，因此具有光可交聯的特性。此分散劑的合成分兩步驟:首先是以穩定自由基聚合法來製備styrene-methacrylate的高分子型碳黑分散劑。為了使得此分散劑具有光可交聯的性質，在第二步驟，我們使用氨基鉀酸酯連結反應(urethane linkane)將methacrylate 官能基接枝於先前合成的分散劑中。此外，另一種新合成的碳黑分散劑也很有趣，因為它同時擁有光可交聯的特性以及鹼性水溶液可溶解的特性，因此可以使用微影製程來製備微結構圖案。此種分散劑的合成也是兩步驟:首先藉由bisphenol-A epoxy diacrylate 以及benzophenone tetracarboxylic dianhydride來製備鹼可溶解之光可交聯樹酯。之後為了使得此樹酯具有分散碳黑的能力，此樹酯與一個含有異氰酸甲酯官能基的單體再更進一步進行反應，最後獲得一光可交聯以及鹼可溶解之碳黑分散劑。 之後，將上述的碳黑分散液加入光起始劑以及光可交聯樹酯(如果是使用光可交聯以及鹼可溶解之碳黑分散劑，則只要添加光起始劑)，即可獲得碳黑光阻。然而，由於碳黑的高度吸收光性以及無法溶於任何溶液中的特性，使得碳黑光阻的光敏感性與顯影能力大大的受到碳黑影響而下降。因此要使用低曝光能量來製備具有高遮光性與高解析度之黑色矩陣是一件非常不容易的工作。有鑑於此，光起始劑以及光可交聯樹酯的選擇變的非常重要。在光起始劑方面，我們研究不同光起始劑的吸光特性以及測量在有碳黑的情況下的樹酯的光聚合速率，以選擇最適合的光起始劑。在光可交聯樹酯方面，由於考慮到環保因素，我們合成新型鹼可溶解的光可交聯樹酯，主要是因為他們可以使用非毒性的鹼性顯影液來製備微圖案。論文中討論這些樹酯的光敏感性以及酸基的含量對於黑色矩陣的圖案形狀以及所需要的曝光能量消耗的效應。最後，使用上述所配置的碳黑光阻，在曝光能量為50-200mJ/cm2的微影製程條件下，我們成功的在玻璃基板上製備光學密度為4μm-1以及解析度為10μm的黑色矩陣。 玻璃基板以及黑色矩陣之間的黏著性也是非常重要的。但是，在彩色濾光片的製程中，玻璃基板以及黑色矩陣之間的黏著性在氧化銦錫(ITO)濺鍍製程後大大的下降。為了解決這個問題，本論文中，我們合成了一個新型光可交聯之矽氧烷偶合劑，其用途是添加於碳黑光阻中當作一種黏著促進劑。此種黏著促進劑是bisphenol-A epoxy diacrylate的氫氧基與3-(isocyanatopropyl)-triethoxysilane的異氰酸甲酯官能基反應所得到的產物。由於此種黏著促進劑同時擁有壓克力基以及矽氧烷基團，因此在紫外光曝照下會交聯，在高溫的環境下可與玻璃基板產生共價鍵。本研究探討此種黏著促進劑在氧化銦錫(ITO)濺鍍製程之前或是之後對於玻璃基板與黑色矩陣之間的黏著力的影響。 在第二部份中，首先，我們使用光-微差掃描熱量計(photo-DSC)來探討鹼可溶解之光可交聯樹酯的光聚合動力學行為，並提出了一個新的方法(結合了暗聚合反應以及擬穩定平衡假設)可以用來計算出propagation、bimolecular termination、monomolecular termination速率常數以及正在成長中的自由基濃度與反應程度之關係。從實驗結果我們發現光聚合反應強烈的受到樹脂以及光起始劑中的極性官能基的影響，並且深入的討論極性官能基對於反應速率常數以及起始劑效率的影響。 在合成styrene-methacrylate共聚合物實驗中，我們發現只有在高styrene的含量的時候，才能成功的使用穩定自由基聚合法來製備styrene-methacrylate的高分子型碳黑分散劑。因此我們提出了一個新的動力模型，其可用來解釋為何穩定自由基聚合法總是無法使用在壓克力單體上。另外，我們還發現添加少樣的極性溶劑可以增加壓克力單體的聚合速度。最後，從動力模型以及實驗結果，我們也計算並討論穩定自由基聚合法中的反應速率常數。

Carbon black photo-resist (CB PR), containing CB, CB dispersant, photo-curable resins, adhesion promoter, photo-initiator, and solvent, was developed for production of high resolution of black matrix (BM) which is an important light-shielding element on the color filter in liquid crystal display (LCD) industry. This work was divided into two parts: (1) the synthesis and function of each ingredient in CB PR and (2) the kinetic behaviors of photo-polymerization and TEMPO-mediated polymerization related to the compounds synthesized in the first part. In the first part, CB was first treated by CB dispersant in order to prepare a high loading of CB dispersion in an organic solvent (propylene glycol monomethyl ether acetate, PGMEA) up to 10 wt%. Three different kinds of dispersants were taken separately to disperse CB, a commercialized dispersant and two newly synthesized dispersants. These three CB dispersants were effectively adsorbed onto CB by the interaction between amino-containing anchoring groups of dispersant and carboxylic acid group on CB surface. They had a moderate chain length to provide a steric repulsion for CB. In addition, the influences of amount and structure of these dispersants on the stability and light-shielding property of CB were discussed. Among these dispersants, one of the newly synthesized dispersants having (meth)acrylate group is an UV-curable CB dispersant, which was synthesized by a two-step process. First, a styrene-(meth)acrylate living copolymer was synthesized as a CB dispersant by TEMPO-mediated living polymerization. In the second step, to render the UV-curable property, additional (meth)acrylate groups were grafted onto the prepared CB dispersant by an urethane linkage reaction. The other newly synthesized CB dispersant was also interesting because it exhibited both UV-curable and alkali-soluble properties, which was capable of forming micro-patterns through an UV-lithographic process. This dispersant was also synthesized by a two-step process. First, UV-curable and alkali-soluble resins were synthesized by the reaction of bisphenol-A epoxy diacrylate with benzophenone tetracarboxylic dianhydride at different molar ratios. Second, to be able to disperse CB particles, these resins were further reacted with an isocyanate-containing methacrylate monomer to produce effective dispersants. Afterwards, CB PRs were prepared by adding photo-initiator and with or without photo-curable resins into the above CB dispersions. However, it was not easy to prepare a BM with both a high opacity and a good resolution upon a low irradiation energy of UV light. This is because CB is a strong light-shielding material which would reduce the photo-sensitivity of CB PR. Besides, the developability of CB PR was strongly retarded by CB since CB can not be soluble in any solvent. In view of this, the selections of photo-initiator and photo-curable resins are critical because they affect the lithographic performance of CB PR. Several photo-initiators were evaluated with respect to their light absorbance and the rate of photo-polymerization in the presence of CB. In addition, several new photo-curable resins were synthesized in this work. UV-curable and alkali-soluble resins were tailored because they can form patterns by an environmental-friendly alkali developer. The influences of photo-sensitivities and concentration of carboxylic acid groups of these resins on the appearance of BM patterns and the energy consumption of UV light were discussed. Finally, a BM with both a high optical density of 4μm-1 and resolution of 10 μm in size upon irradiation of 50-200 mJ/cm2 was successfully produced by using the aforementioned CB PRs through an UV-lithographic process. In addition, the adhesion strength between BM and glass substrate was studied. In the manufacturing process of color filter, the adhesion strength between the BM and glass substrate largely decreased after the ITO sputtering process. To overcome this problem, in this work, a newly synthesized UV-curable silane coupling agent as an adhesion promoter was added into a CB PR. This adhesion promoter was synthesized by the reaction between the hydroxyl group of bisphenol A epoxy diacrylate and the isocyanate group of 3-(isocyanatopropyl)-triethoxysilane. This adhesion promoter containing both acrylate and triethoxysilane groups can be cured upon UV irradiation and form a strong covalent bond with the glass substrate at high temperature, respectively. The influence of this adhesion promoter on the adhesion strength between BM and glass substrate before and after ITO sputtering process was discussed. In the second part, the kinetic behaviors of photo-polymerization of UV-curable resins with carboxylic acid and amino functional groups were investigated. The rate of polymerization and extent of reaction were monitored by using a photo differential scanning calorimeter. A new method combining dark polymerization with pseudo steady state assumption of growing radicals was presented in order to calculate the kinetic constants for propagation, bimolecular termination, monomolecular termination, and the concentration of growing radicals of each resin as a function of extent of reaction. According to the experimental results, it was found that the photo-polymerization was strongly influenced by both functional groups of resins and photo-initiators. The influences of functional groups on the kinetic rate constants and initiator efficiency were discussed in depth. For the CB dispersant synthesized by TEMPO-mediated copolymerization of styrene and (meth)acrylate monomers, the successful living character was observed only at high styrene molar fraction in feed. In view of this, a new kinetic model was established in order to explain the retardant mechanism of the living polymerization of (meth)acrylate. Besides, it was found that TEMPO-mediated polymerization of acrylate could be improved by adding a small amount of polar solvent, DMF (N,N-dimethylformamide) as a rate-enhancement agent. Finally, by using this kinetic model and experimental results, the kinetic rate constants in the TEMPO-mediated polymerization were then calculated and discussed.