content_image/944796.jpg content_image/944797.jpg content_image/944798.jpg content_image/944800.jpg content_image/944799.jpg
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-continued 

(a2-5-3) 

(a2-5-4) 

(a2-5-5) 

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[0178] In the component (Al), as the structural unit ( a2), one type of structural unit may be used, or two or more types may be used in combination. 

[0179] As the structural unit ( a2), at least one structural unit selected from the group consisting of formulas ( a2- l) to ( a2- 5) is preferable, and at least one structural unit selected from the group consisting of formulas (a2-l) to (a2-3) is more preferable. Of these, it is preferable to use at least one struc› tural unit selected from the group consisting of structural units represented by formulas (a2-l-l), (a2-l-2), (a2-2-l), (a2-2-7), (a2-3-l) and (a2-3-5). 

[0180] In the component (Al), the amount of the structural unit (a2) based on the combined total of all structural units constituting the component (Al) is preferably 5 to 60 mo! %, more preferably 10 to 50 mo! %, and still more preferably 20 to 50 mo!%. When the amount of the structural unit (a2) is at least as large as the lower limit of the above-mentioned range, the effect of using the structural unit (a2) can be satisfactonly achieved. On the other hand, when the amount of the struc› tural unit (a2) is no more than the upper limit of the above› mentioned range, a good balance can be achieved with the other structural units. 

[0181] (Structural Unit (a5)) 

[0182] The structural unit (a5) is a structural unit repre› sented by general formula (a5-l) shown below. 

[Chemical Formula 28] 

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-continued 

(a2-5-6) 

(a5-1) 

