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In the formulae, each R$_{3 }$independently represents a hydro› gen atom or a monovalent organic group. R$_{3}$s may combine with each other to form a ring. 

Each R$_{4 }$ independently represents a monovalent organic group. R$_{4}$ s may combine with each other to form a ring. R$_{3 }$ and R$_{4 }$ may combine with each other to form a ring. 

Each Rs independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkenyl group or an alkynyl group. At least two Rss may combine with each other to form a ring, provided that when one or two of three Rss are a hydrogen atom, at least one of the remaining Rss represents an aryl group, an alkenyl group or an alkynyl group. 

The group capable of decomposing by the action of an acid to produce an alcoholic hydroxy group is also preferably represented by at least one formula selected from the group consisting of the following formulae (II-5) to (II-9): 

In the formulae, R$_{4 }$ has the same meaning as in formulae (II-1) to (II-3). 

Each R$_{6 }$ independently represents a hydrogen atom or a monovalent organic group. R$_{6}$s may combine with each other to form a ring. 

The group capable of decomposing by the action of an acid 55 to produce an alcoholic hydroxy group is more preferably represented by at least one formula selected from formulae (II-1) to (II-3), still more preferably represented by formula (II-1) or (II-3), yet still more preferably represented by for› mula (II-1). 60 

R$_{3 }$ represents a hydrogen atom or a monovalent organic group as described above. R$_{3 }$ is preferably a hydrogen atom, an alkyl group or a cycloalkyl group, more preferably a hydrogen atom or an alkyl group. 

The alkyl group of R$_{3 }$ may be a linear or branched-chain 65 alkyl group. The carbon number of the alkyl group ofR$_{3 }$ is preferably from 1 to 10, more preferably from 1 to 3. 

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Examples of the alkyl group ofR$_{3 }$ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group and an n-butyl group. 

The cycloalkyl group ofR$_{3 }$ may be monocyclic or polycy› clic. The carbon number of the cycloalkyl group of R$_{3 }$ is preferably from 3 to 10, more preferably from 4 to 8. Examples of the cycloalkyl group ofR$_{3 }$include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a norbornyl group and an adamantyl group. 

In formula (II-1), at least either one R$_{3 }$ is preferably a monovalent organic group. When such a configuration is employed, particularly high sensitivity can be achieved. 

R$_{4 }$represents a monovalent organic group. R$_{4 }$ is preferably an alkyl group or a cycloalkyl group, more preferably an alkyl group. These alkyl group and cycloalkyl group may have a substituent. 

The alkyl group ofR$_{4 }$ preferably has no substituent or has one or more ary 1 groups and/ or one or more sily 1 groups as the substituent. The carbon number of the unsubstituted alkyl group is preferably from 1 to 20. The carbon number of the alkyl group moiety in the alkyl group substituted with one or more aryl groups is preferably from 1 to 25. The carbon number of the alkyl group moiety in the alkyl group substi› tuted with one or more silyl groups is preferably from 1 to 30. Also, in the case where the cycloalkyl group of R$_{4 }$ does not have a substituent, the carbon number thereof is preferably from 3 to 20. 

Rs represents a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkenyl group or an alkynyl group. However, when one or two of three Rss are a hydrogen atom, at least one of the remaining Rss represents an aryl group, an alkenyl group or an alkynyl group. Rs is preferably a hydro- gen atom or an alkyl group. The alkyl group may or may not have a substituent. When the alkyl group does not have a substituent, the carbon number thereof is preferably from 1 to 6, more preferably from 1 to 3. 

R$_{6 }$ represents a hydrogen atom or a monovalent organic group as described above. R$_{6 }$ is preferably a hydrogen atom, an alkyl group or a cycloalkyl group, more preferably a hydrogen atom or an alkyl group, still more preferably a hydrogen atom or an alkyl group having no substituent. R$_{6 }$is preferably a hydrogen atom or an alkyl group having a carbon number of 1 to 10, more preferably a hydrogen atom or an alkyl group having a carbon number of 1 to 10 and having no substituent. 

Examples of the alkyl group and cycloalkyl group ofR$_{4}$ , Rs and R$_{6 }$ are the same as those described for R$_{3 }$ above. 

Specific examples of the group capable of decomposing by the action of an acid to produce an alcoholic hydroxyl group are illustrated below. 

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