query performance

I have this query in a table with 150 thowsand tuples and it takes to long

t_documentcontent._id AS _id
FROM t_documentcontent LIMIT 50 OFFSET 80000

here is the explain output

"Limit (cost=100058762.30..100058799.02 rows=50 width=58) (actual time=
19433.474..19433.680 rows=50 loops=1)"
" -> Seq Scan on t_documentcontent
(cost=100000000.00..100110772.07rows=150807 width=58) (actual time=
53.934..19402.030 rows=80050 loops=1)"
"Total runtime: 19433.748 ms"

here the table structure

CREATE TABLE t_documentcontent(
_id varchar(60) NOT NULL,
_filesystem varchar(60) NOT NULL,
_parent varchar(60) NOT NULL,
_document varchar(60) NOT NULL,
_title varchar NOT NULL,
_resume varchar,
_content varchar,
_lang integer NOT NULL,
_creationdate timestamp NOT NULL DEFAULT now(),
_updatedate timestamp NOT NULL DEFAULT now(),
_indexeddate timestamp NOT NULL DEFAULT now(),
CONSTRAINT documentcontent_pkey PRIMARY KEY (_id),
CONSTRAINT documentcontent_filesystem_fkey
FOREIGN KEY (_filesystem) REFERENCES t_filesystem(_id) ON UPDATE
CASCADE ON DELETE NO ACTION,
CONSTRAINT documentcontent_parent_fkey FOREIGN KEY (_parent) REFERENCES
t_node(_id) ON DELETE NO ACTION,
CONSTRAINT documentcontent_document_fkey
FOREIGN KEY (_document) REFERENCES t_node(_id) ON UPDATE CASCADE ON
DELETE NO ACTION,
CONSTRAINT documentcontent_lang_lang_fkey FOREIGN KEY (_lang) REFERENCES
t_lang(_id)) WITHOUT OIDS;

Any ideas for improve this query performance.