hereinafter , the present disclosure will be further illustrated in conjunction with specific examples . it should be understood that these examples are only used for illustrating , not limiting , the protection scope of the present disclosure . hereinafter , the embodiments of the present disclosure will be illustrated through specific instances . those skilled in the art may easily understand other advantages and effects of the present disclosure through the disclosure of the specification . the present disclosure may be implemented or applied through other different preferred embodiments . various details in the present description may also be modified or changed based on different views or applications without departing from the spirit of the present disclosure . it should be noted that in the following examples , processing devices or means not explicitly labeled all adopt conventional devices or means in the art ; all pressure values and ranges refer to relative pressures . the following examples use silica sol ( mcs - s10 , shanghai xinanna electronic technology co ., ltd ), γ -( 2 , 3 - epoxypropoxy ) propyltrimethoxysilane ( kh - 560 , hangzhou jessica chemical co ., ltd ), vinyltriethoxysilane ( kh - 188 , hangzhou jessica chemical co ., ltd ), polyving akohol ( 1788 , sinopec shanghai ( jinshan ) petrochemical company limited ), acrylic resin ( syntran 404 , yintai polymer trade ( shanghai ) co ., ltd ), polyurethane ( pu037 , shanghai yuchi import & amp ; export co ., ltd ), styrene - acrylic resin ( syntran 1671 , yintai polymer trade ( shanghai ) co ., ltd ), epoxy resin ( carapol wep 2308 , yintai polymer trade ( shanghai ) co ., ltd ). besides , it should be understood that one or more method steps in the present disclosure do not exclude existence of other method steps before and after the combining step , or other method steps may also be inserted between these explicitly mentioned steps , unless otherwise explained ; it should also be understood that the combination and connection relationships between one or more devices / means mentioned in the present disclosure do not exclude existence of other devices / means before and after the combined device / means or other device / means may be inserted between two devices / means explicitly mentioned here , unless otherwise indicated . moreover , unless otherwise indicated , serial numbers of respective method steps are only for facilitating discrimination between respective method steps , not arrangement order for limiting respective method steps or limiting the implementable scope of the present disclosure ; change or adjustment of their relative relationships should also be regarded as implementable scope of the present disclosure without substantively changing the technical content . add 1 kg silica sol ( solid content is 30 %; its particle size is 10 nm ) into a three - mouth flask and stir it ; under a room temperature and a constant stirring condition , take 15 . 3 g γ -( 2 , 3 - epoxypropoxy ) propyltrimethoxysilane and drop it into the silica sol to stir and mix , the dropping rate being 7 ml / min , the duration of stirring and mixing being 1 h ; continue stirring to react for 48 h , obtaining a mixed solution . under a constant stirring condition , drop 100 g polyurethane into the mixed solution to stir and mix , the dropping rate being 10 ml / min , the duration of stirring and mixing is 1 h ; continue stirring to react for 2 h , finally preparing a film - forming silica sol sample 1 #. in the film - forming silica sol sample 1 #, the silica sol occupies 89 . 6 %, the γ -( 2 , 3 - epoxypropoxy ) propyltrimethoxysilane occupies 1 . 4 %, and the polyurethane occupies 9 %. add 1 kg silica sol ( its solid content is 30 %,; its particle size is 10 nm ) into a three - mouth flask and stir it ; under a room temperature and a constant stirring condition , take 15 . 3 g γ -( 2 , 3 - epoxypropoxy ) propyltrimethoxysilane and drop it into the silica sol to stir and mix , the dropping rate being 7 ml / min , the duration of stirring and mixing being 1 h ; continue stirring to react for 48 h , obtaining a mixed solution . under a constant stirring condition , drop 150 g polyurethane into the mixed solution to stir and mix , the dropping rate being 10 ml / min , the duration of stirring and mixing is 1 h ; continue stirring to react for 2 h , finally preparing a film - forming silica sol sample 2 #. in the film - forming silica sol sample 2 #, the silica sol occupies 85 . 8 %, the γ -( 2 , 3 - epoxypropoxy ) propyltrimethoxysilane occupies 1 . 3 %, and the polyurethane occupies 12 . 9 %. add 1 kg silica sol ( its solid content is 30 %; its particle size is 10 nm ) into a three - mouth flask and stir it ; under a room temperature and a constant stirring condition , take 15 . 3 g γ -( 2 , 3 - epoxypropoxy ) propyltrimethoxysilane and drop it into the silica sol to stir and mix , the dropping rate being 7 ml / min , the duration of stirring and mixing being 1 h ; continue stirring to react for 48 h , obtaining a mixed solution . under a constant stirring condition , drop 300 g polyurethane into the mixed solution to stir and mix , the dropping rate being 10 ml / min , the duration of stirring and mixing is 1 h ; continue stirring to react for 2 h , finally preparing a film - forming silica sol sample 3 #. in the film - forming silica sol sample 3 #, the silica sol occupies 76 %, the γ -( 2 , 3 - epoxypropoxy ) propyltrimethoxysilane occupies 1 . 2 %, and the polyurethane occupies 22 . 8 %. add 1 kg silica sol ( its solid content is 30 %; its particle size is 10 nm ) into a three - mouth flask and stir it ; under a room temperature and a constant stirring condition , take 15 . 3 g γ -( 2 , 3 - epoxypropoxy ) propyltrimethoxysilane and drop it into the silica sol to stir and mix , the dropping rate being 7 ml / min , the duration of stirring and mixing being 1 h ; continue stirring to react for 48 h , obtaining a mixed solution . under a constant stirring condition , drop 500 g polyurethane into the mixed solution to stir and mix , the dropping rate being 10 ml / min , the duration of stirring and mixing is 1 h ; continue stirring to react for 2 h , finally preparing a film - forming silica sol sample 4 #. in the film - forming silica sol sample 4 #, the silica sol occupies 66 %, the γ -( 2 , 3 - epoxypropoxy ) propyltrimethoxysilane occupies 1 %, and the polyurethane occupies 33 %. add 1 kg silica sol ( its solid content is 6 %; its particle size is 15 nm ) into a three - mouth flask and stir it ; under a room temperature and a constant stirring condition , take 15 . 3 g vinyltriethoxysilane and drop it into the silica sol to stir and mix , the dropping rate being 6 ml / min , the duration of stirring and mixing being 0 . 5 h ; continue stirring to react for 1 h , obtaining a mixed solution . under a constant stirring condition , drop 500 g acrylic resin into the mixed solution to stir and mix , the dropping rate being 8 ml / min , the duration of stirring and mixing is 0 . 5 h ; continue stirring to react for 1 h , finally preparing a film - forming silica sol sample 5 #. in the film - forming silica sol sample 5 #, the silica sol occupies 66 %, the vinyltriethoxysilane occupies 1 %, and the acrylic resin occupies 33 %. add 1 kg silica sol ( its solid content is 40 %; its particle size is 6 nm ) into a three - mouth flask and stir it ; under a room temperature and a constant stirring condition , take 15 . 3 g low molecular weight polyvinyl alcohol and drop it into the silica sol to stir and mix , the dropping rate being 8 ml / min , the duration of stirring and mixing being 2 h ; continue stirring to react for 72 h , obtaining a mixed solution . under a constant stirring condition , drop 500 g styrene - acrylic resin into the mixed solution to stir and mix , the dropping rate being 12 ml / min , the duration of stirring and mixing is 2 h ; continue stirring to react for 5 h , finally preparing a film - forming silica sol sample 6 #. in the film - forming silica sol sample 6 #, the silica sol occupies 66 %, the low molecular weight polyvinyl alcohol occupies 1 %, and the styrene - acrylic resin occupies 33 %. apply pure silica sol without being processed by a modifying agent and a film - forming auxiliary onto an aluminum plate surface ; after the membrane layer is naturally dried , coating 1 is formed . the specific result was shown in fig1 . apply the film - forming silica sol sample 1 # onto an aluminum plate surface by a coating machine ; after the membrane layer is naturally dried , coating 2 is formed . the specific result was shown in fig2 . apply the film - forming silica sol sample 2 # onto an aluminum plate surface by a coating machine ; after the membrane layer is naturally dried , coating 3 is formed . the specific result was shown in fig3 . apply the film - forming silica sol sample 3 # onto an aluminum plate surface by a coating machine ; after the membrane layer is naturally dried , coating 4 is formed . the specific result was shown in fig4 . apply the film - forming silica sol sample 4 # onto an aluminum plate surface by a coating machine ; after the membrane layer is naturally dried , coating 5 is formed . the specific result was shown in fig5 . test the hardness of coatings 1 - 5 after natural drying in application examples 1 - 5 . the test results are illustrated in table 1 . as shown in table 1 that compared with coating 1 without adding the modifying agent and film - forming auxiliary , coatings 2 - 5 added with the modifying agent and film - forming auxiliary had a higher hardness ; however , the more film - forming auxiliary amount was added , the lower the dried membrane layer hardness was ; therefore , compared with coating 5 , coating 4 had a better hardness . meanwhile , as shown in fig1 - 5 that by obtaining the glossiness and adhesive force related information through naked - eye observation and key scratching , compared with coating 1 without adding the modifying agent and the film - forming auxiliary , the glossiness of the coating increased with the amount of film - forming auxiliary being added , and the transparency of the membrane layer gradually increased , i . e ., the more the film - forming auxiliary was added , the better the glossiness was ; therefore , coating 5 has a good glossiness . meanwhile , the stronger the binding force among the coating and the membrane layer and the matrix was , the better its adhesive performance was ; while the stronger binding force among the coating layer 5 and the membrane layer and the matrix indicates a good adhesive performance . in view of the above results , after the modifying agent and the film - forming auxiliary are added , only when an appropriate film - forming auxiliary amount is added , can the hardness , glossiness , and adhesive force of the coating reach an optimum value . therefore , the present disclosure effectively overcomes various drawbacks in the prior art and thus has a high industrial utilization value . the embodiments above only exemplarily illustrate the principle and effect of the present disclosure , not for limiting the present disclosure . any person familiar with this technology may modify or change the examples above without departing from the spirit and scope of the present disclosure . therefore , any modification or change implemented by any person skilled in the art without departing from the spirit and technical idea of the present disclosure should be included within the claims of the present disclosure .