CA2085696A1

CA2085696A1 - Primer for phenyl-based silicone pressure-sensitive adhesives

Info

Publication number: CA2085696A1
Application number: CA002085696A
Authority: CA
Inventors: Stuart R. Kerr, Iii
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1992-01-03
Filing date: 1992-12-17
Publication date: 1993-07-04
Also published as: CA2082445A1; JP3527257B2; US6602597B1; JPH05255648A

Abstract

PATENTS

ABSTRACT OF THE DISCLOSURE
Silicone primer compositions that provide excellent anchorage for phenyl-based silicone pressure sensitive adhesive prepared tape. The compositions comprise a phenyl-modified siloxane component such as a dimethyl-diphenyl siloxane component. The relative amount of phenyl substituents in the phenyl-modified primer matches the mole percent or phenyl substituents a dimethyl, 5.3 mole percent diphenyl, silanol chain stopped silicone gum. Very thin layers of the primer are used between a substrate and a pressure sensitive adhesive. The primer compositions virtually eliminate all tendencies of phenyl-based silicone PSA prepared tape to delaminate.

Description

208~696 PA~ENTS

PRINER FOR PHENY~-BASED SILICONE
P~ESSURE-SENSITIVE ADHESIVES

F~D QF T~ INVEN~3ON
Th- pr --nt invontlon r-lat-- to p ~-uro son-ltlv- a~h -lv- tap ~ and, mor- pareleul~rly, to ~ eon- compo-ltlon- ~ult~ble for ~or~lng prl~or l~y-r- for pr --ur- ~-n-ltl~e ~dh~-~v-- Th- pr --nt in~onelon furthQr relate~ to ~ pr~m r and adhe~v~
~y-tem for ~ pre--ur ~on-lt~v adh -l~ tap~ wh-roln th prlm-r and adh -iv- eompo-ltlon- ~ach co~prl~- a s~llar ph-nyl-modlf~d ~llleon co~pon nt L = ~
S~lieon- pr---ur ---n-ltlv- ~dh -iv - (PSA~) ar prl~arily co~po--d of a ml~t~r~ of hl~h mol~cul~r w~lghe~ 311anol-functlon~l o n ano~llo~n polymar~ And ~llAnol-funetlonal polym~r r~-ln~ T~ polymertr~Jln 2 6o5~7~FlT~Sol bl~nd~ are often furth~r b~tch-co~pound-d in 801v~nt Jolutlon by th- cataly2æd condensation react1on (ln ~tu) of tho silanol-functional reactant~ thyl-based silicono PSA~ incorporato a polymor osmponent b~--d on repeatlng di~ethyl ~ilo%ane buildlng block~.
PhQnyl-ba~Od 5ili~0n8 PSA's incorporate a polymer component ba~d on a c~natlon of both dimethyl ~iloxane and diphenyl silo~an~ bu~lding blocks. Tho pr~ence of pendent ph nyl funct~onal~y in th~
~ con~ polymQr bac~bon~ lnc~oa~ both the h~gher tq p rature p for~enc- ~nd tb~ el~ctr~cal r~ tanc~
pJ~p rtl-~ of~tb- ad~ ~lv~.l S~licon- P5A'~ ar UJOd for co~ting high-temp raturQ fiLo sub~trateJ, al~o called baoe film~.
~uch aJ polye~ter. polyother~ide, polyimide, PTP~
(polytetr~fluoroethylenQ)~ and FEP (fluoroethylene propyleno~ in the prep~ration of high-performance industrial tape~. ThQ~o _apes may be us-d for electrical inJulatlon, electronic a~ombly ma~king, 208~69~ j 3 P~N~
60S~-1401 fl~me and plasma ~pray masking, EMI/RPI shielding, and splicing opQrations.
ThQse processQd tapQs are ~elf-wound, resulting in a number of dispQnsing is~ue~ for the tape manufacturer. Handling difficulties are created a~ a result of insufficient "anchorage~ of the adhe~ive layer to the ~ubstr~te film. When the tapa is unwrapped during slitting opQratLons or in automated dispensing operations, the adhe~ive may delaminate from the base film and transfer to the baek-~ide of the wrapped tape, splittinq the adhe~ive lay~r. This phenomenon i~ known as ~legging~ Webbing~ phenomena may also occur during slitting oper~tlons when the adhesive layer reJistJ clean sl~tting, reaultlng in an adhesive ~webY that promote~ delamination off the base film along the slit-edge~.
~ oth "legging" and "webbing~ can be ellminated if the adhe~ive i9 suffici~ntly primer-bonded to the ~urface of the film sub~trate. A primer which ha~ baen previously applied to the surface of a film substrate acts as a tie-layer for Yecurely anchoring the adhesive layer to the substrate.
Typically, the surface energy of a silicone PSA i3 extremely low, usually within the range of 20-26 mNm-l.
This surface energy is in the ~ame general range as traditional sil~cone release coating~ which use this unique property for providing an easy-release surface for label stock. Organic-based (non-silicone) PSA's are high surface energy systems and consequently will not ~wat out~ onto lower energy surfaces, thus accountLng for the ease-of-release characteristic. On the other hand, silicone PSA's do not readily release from a sllicone relea~e coating because their low surface energy allows them to ~wet out~ onto the 208~9~

4 P~E~
60S~-1401 surface of tho releHse coat. rt has beon found that some silicono releaJe coatings, such aJ thoJe havlng a silanol gum with a dimQthyl-slloxane polymer component, make excellent prlm~r~ for mo~t silicone PSA ~ ln the preparation of high-performancQ indu~tr'al tape. Such ~ilicone relea~e coating~ are widely used in industrial tape~ for priming silicone PSA fllm~tock.
Although the techn'que of priming with primer~
compri~ing a dimethyl~$10xane silsnol gum ha~ be0n a ~tandard in the indu~try for many yeax~, it ha~ been found in practice to be only fea~ible for methyl-ba~ed ~ cone PSA 8. However, the~e pr~mer~ and other simllar commer~ially available primar~ do not provide the anchorage neces~ary for phenyl-ba~ed ~ilicone PSA 8. A need therefore Qxlsts for an effective primer for phenyl-ba~ed PSA 8.

SU~ARY OP~
The pre~ent invention relatQJ to ~ilicone primer compositlons that provide excellent anchorage for phenyl-ba~ed sllicone pre~ure ~en~itive adhe~ive~ used in the preparation of PSA tapeo. The primer compositlonJ compri3e a silanol chain~topped phenyl-modified siloxane gum component, preferzbly a dimethyl-diphenyl siloxane gum component. The relative amountof phenyl sub~tituentJ ln the phenyl-modified sillcone primer may vary depending upon the relativs amount of phenyl substituQnt~ pre~ent in a pro~ure sensitive adhe~'ve composltlon whlch i8 to be u~ed in con~unction wlth the primer.More preferably, the Amount of phenyl substltuents in the primer matche~ the amount of phenyl sub~tltuentJ ~n the adhe~lve. Mo~t proferably, the amount of phenyl substltuents in the primer is with'n 208~69B

PAT~pT~

about ten percent of the amount of phenyl ~ubstituents in the adhe~ive.
According to OnQ embodiment, the ~mount of phenyl subRtituQnts in each of the primer and adhe~ive i8 preferably between about 5.0 and about 5.5 mole parcent. One particular primer and adhesi~Q 8y8tem in accordance with an embodiment of the presQnt invention comprises a dimethyl, 5.3 mole percent diphenyl, ~ilanol chainstopped silicone gum in both the primer and the ~dhe~ve.
Very thin layers of the primer are used between the adhe~lve compo~ition and a supporting substrate.
The primer compo~ition~ of the pre~ent invention, when used according to the present invention, virtu~lly eliminatQ all tendencie~ of phenyl-ba~ed PSA prepared tape to delaminate.

BR~EF DESCRIPT~QN O~ ~H~ DR~WINGS
Fig. 1 is a graph -~howing the generated adhesive web width of various primed PSA's when sub~ected to a slit-Qdge w~b genQration test.

DE~AILED ~ÇR~IIn~LQ~ INVENTION
The primer compo~itions of the prQsent invention have been developed to be used for priming substrate~
surfacQJ 80 as to receive a phenyl-modified ~ilicone pressure sensitive adhesivQ composition. According to an embodiment of the prQsent invention the prLmer comprlses a silanol chainstopped phenyl-modified siloxane gum which haJ a total phenyl substituent mole percentage which ~ubstantially matches the mole percenthge of phenyl substituQnt~ in the adhesive. The phenyl-modified component of the primer is preferably the ~ame as the phenyl-mcdified componQnt of the 208~69~

6 ~ N~

adhesive. The relative amount of phenyl substituents in each of the primer and adhesive should also be the same although an amount in the primer which i8 within ten percQnt of the amount in the adhasive is still provides excellent result~.
According to an embodiment uperior adhe~ive tape systQms can be developed from primer and adhQsive compositions which each have a siloxane ~um containing from about 5.0 to about 5.5 mols percent phenyl substltuents. GUm~ having about five percent phenyl ~ub~tituents are preferrQd. GUmJ h~ving about 5.3 and 5.5 mole percent diphenyl sub~tituents have proven to provide effective primer layer~ for phenyl basQd siliconQ PSA's.
The silanol end groups of the chain~ ara cros~-linked, aftar application to a substrate, by a tin-catalyzed ~ilanol-hydride reaction. A tin catalyst may be provided in the dispersant of the primer composition to enable the silanol-hydrid2 reaction. Cro~s-linking along the backbone of each chain i8 initi~ted by a peroxide initiator which become~ available from an adheJive composition applied to the primed substrate.
Once the adhesive i9 applied to the primer layer, solv4nt and peroxide from the adhesive 8well8 into the primer layer and initiates backbone cros~-linking between the primer chain~, between the adhesive chain~, and between the primer and the adhesive to at least partially cross-link the primer layer to the adhesive layer.
ThQ phenyl ~ubatituents on the polyslloxane backbone may be methyl/phenyl or diphenyl group~. The silicone gumJ usually also contain dimethyl substituent group~. The siloxane component preferably comprises a ~ilanol chainstopped ailicone gum having a molecular 208~69~

7 _EaIæNTS
60SI~
weight range of from about 300,000 to about 600,000.
The re~in/gum silicone PSA composition typlcally ha~ a vi~cosity of about ~0,000 to about 100,000 cp~ when preJent in a solution of about 55 percent ~olid~ in xylene.
The primer compositions according to an embodiment of the preR~nt inv~ntion further contain a cros~-linker dispersed in an appropriate solvQnt. The primer compositions are dispersed in a Yolvent to facilitate thin coating. One particularly useful solvent i8 a 50~50 blend of toluene and hexane, although other solvant~ may be usQd. The ~mount of cros~-linker may vary but is preferably about four percent the weight of the gum.
In accordance with a preferred embodi~ent of the present Lnvention, and in previous primer application technique~, a very thin layer of primer i~ coated onto a tape sub~trate, such as a sheet of polyester, polyimide or polytetrafluoroethylene having a thicknes~
of about one to about sQven mils. Generally, polyest~r and polyimide films are used at a thicknQs~ of about one to about two mils wherQas PTF~ ~ubstrates are u~ed at a thicknes~ of about two to about seven mil3.
The primer compositions of tha pre~ent invention may be coated, i.e., applied over ~upportLng film substrates by vAriOUs methods; however, application with a #8 or #12 meyer rod ha~ proven to be a simple method for providing a uniform thin layer. The primer layer should preferably be applied at a coverage of about O.2 to about O.S pound3 per re~m. The coverage may vary due to the specific primer composition but i~
most preferably about 0.3 pounds per ream for a primer compo~Ltion having a phenyl-modified siloxane component with about f iVQ mole percent phenyl sub~tituents.

208~696 8 PAT~

Thlnner layers tend to adhero better to substrateJ due to an unexplalned phenomena which most likely re~ults from Van der Waals, dipole, induced dipole, hydrogan bonding or other intr~molecular forees.
S Ater application to thQ ~ubstrate, the primor completes cross-linking at its silanol functional end ~roups in thQ pre~enc~ of a tin cataly~t. A prepared pres~ure ~en~itlv~ adhesive i~ th~n applied to the primer co~ted substrate and cured. Tape~ prepared in thls manner nnd incorporating the phenyl ba~ed primers of the pre~ent invention virtu~lly el~minate the tendency of the tape~ to delaminate.
It i~ believed that duQ to tho interfacial compatibilities betweQn th~ phenyl-based 9il ~ cone prlmer of the present invention and the phenyl-based silicone PSA compo~itions to be us~d in con~unction therewith, very strong bonds between the adhe~ive compo-~itlon~ and supporting substrates can be obtalned.
This l~ even more pronounced when the amount of phenyl substituents in each i8 closely matched.
Table I shows the component compositions for two experimentaL primer compo~itions in accordance with embodiment~ of the present invention ~nd for ~ standard methyl-based dimethyl siloxane gum primer. Composition I incorporates 0.5% less methyl hydrogen fluid cros~-link~r than does Composition Ir or thQ Standard.
As used herein "meyer rod" or "Meyer rod" refers to a wire-wound wet film applicator rod. The "Y8" or "~12"
used in conjunction with this term designates the wire size of the wire wound around the rod. Generally the larger the wire size, the thicker the film that is applied. -8 wire has a diameter of 0.008 inches.
il2 wire hdS d diameter of O.OlZ inches.

PA~S

Tt~ PRI~a55~æQS~S

PRIM~RS
Component~, Darts Py weig~ ga~ard dimethyl, 29.25 29.25 5.3 mole percent diphenyl, silanol chain stopped ~licone gum dimethyl ~ilanol ---- ---- 29.25 chain-~topped silicone gu~
methyl hydrogen 1.25 1.75 1.75 flu$d cros~-linker 50/50 blend 69.50 69.00 69.00 toluene/hexane solvent The ~nvent$on may be more fully under~tood with reference to the example~ set forth below.
EXAMPLE I
0.66 gram of a 50% toluene ~olution of dibutyl tin diacetate and 0.66 gram of a cure accalerator comprising a 50~ toluene solution of methyl-2-dimethyl amino ethoxypoly~lloxane chainstopped with trlmothyl~$10xy group~ was added to 13.3 gr~m~ of Compo~ition T. Thi~ activated mixture was then diluted wlth 85.38 gramJ of a 50~50 blend of toluene and hexnne ~olvent~. Tho primer waJ coated and cured onto a varlety of high-temperature film ~ub~trates. (see Table II) pAT~r~_ EXA~oe$ lI
0.66 gram of a 50~ toluene solution of dibutyl tin diacetate and 0.66 gram of a cure accelerator compri~ing a 50~ toluene oolution of methyl-2-dimethyl amino ethoxypolysiloxane cha~nstopped with trimethyl~iloxy groups wa~ added to 13.3 gr~ms of Composition II. This activated mixture was then diluted wlth ~5.38 grams of A 50/50 blend of toluene and hexane solventJ. The primer was coated ~nd cured onto a varlety of high-temperature film substrates.
(see Tabl~
E~ L~-LlL
0.66 gram of a 53~ toluene solutlon of dibutyl tin diacetate and 0.66 gram of a cure accelerator compri~ing a 50t toluene solution of methyl-2-dimethyl amino ethoxypolysiloxane ch~instopped with trimethyL~iloxy groups wa~ added to 13.3 grams of the standard methyl-ba~ed primer. This activ~ted mixture wa~ then diluted with 85.3~ gr~m~ of a 50/50 blend of toluene and hexane solvent~. The primer was coated nnd cursd onto a ~ariety of high-temper~ture film sub~trates. (see Table II) 11 P.~_ ~ PRE~D~S

All Samples Were Cured 20 sec. Q 265-F

P~I ~

Sample Film ~eyer Rod Prepa~atio~ ~lm~ Substr~tQ Number 1 Example I l-mil 12 Polyester 2 Example r l-mil 8 Polyester 3 Example I l-mil 12 Polyimide 4 E~ample I 2-mil 12 PTFE
Example II l-mil 12 Polye~er 6 Ex~mple II l-mil 12 Polyimide 7 Example II 2-mil 12 PTFE

8 Example III l-mil 12 Polyester 9 Example III l-mil 12 Polyimide Example III 2-mil 12 PTFE

The three primer formulations prepared according to Examples I - III were coated and cured into polyester, polyimide and PTFE films as delineated in 2085~96 12 P~NTS

Table II. Two different Meyer rods were employed for applying samplQ prepar~tion~ 1 and 2. It is e~timated that use of the #8 Meyer rod achieveR 8 coatlng weight of 0.3 lbs~ream while use of the #12 Meyer rod achieve~
an e~timated coating welght of 0.6 lb~/ream - these est~mate~ being provided for approx. 4.5% primer solutions onto l-mil polyimide fiLm.
Two peroxide catalyzed Jilicone PSA solutiona were prepared. The fir~t was a phenyl-based ~ilicone PSA
ha~ing a resin to gum r~tio of about 53 to 47. The resln wa~ a polytrimethyl hydro~ilyl silicate MQ
s~loxane re~in having a molecular weight of between about 1500 and 2000. The gum wa~ a dimethyl, 5.3 mole percent diphenyl, polyorgano~iloxane silicone gum having a molecular weight of about 500,000. The silicone PSA solution had a viscosity o about 75,000 cps a~ a solution at 55 percent solid~ in xylene. The sQcond PSA ~ilicone solut10n wao a methyl-based resin/gum silicone PSA having a re~in to gum ratio of about 57 to 43. The resin was a polytrimethyl hydrosilyl silicate MQ ~iloxane resin having a molecula~: weight of between about 1500 and 2000. The gum was a dimethyl substituted polyorgano~iloxane gum having a molecular weight of about 500,000. The ~ilicone PSA ~olution had a viscosity of about 90,000 cpc a~ a solutlon at 60 percent solids in toluene.
Each PSA wa8 catalyzed with 2.0~ benzoyl peroxide relative to the solidJ weight. The~e prepared PSA~s were coated onto the primed and unprimed polyester, poly~mide and PTFE films to achieve a 1.5-mil dry adhe~ive coating thickness. Each coated sample wa~
cured or 90 seconds ~ 95-C (solvent flash), followed by 2 minuteJ ~ 165-C (peroxide cure).

208S69~

13 PaI~NTS_ Cured silicone PSA tape ~mple~ were then e~aluated for anchorage by initiating a ~lit in the tape and then propagating a tear along its length. The width of the generatQd ~dhesiva ~web~ wn~ then ~isually calculated using an inch-~cale rulsr. A poorly anchored pre~sure ~ensitive adha~ive tape will generate a wide adhQsive layer web due to adhesive delam~nation along the slit-edge~. This delamination will ~eed the growing web helping it to resist tearing. Web generation widths of 1/2 inch or le~s indicate acceptable anchor~ge. Web generation width~ of less than 1~8 inch are mo~t de~irable. Web genQr~tion w~dth~ of more than 1/2 ~nch aro generally unacceptable for mo~t application~. The 8UCCQ~ of anchor~e i~
determinQd by the abillty of the primer to pr~vent ~lit-edge del~min~tion and thus its effectivenes~ in eliminating web generation. Table III summariz~s the re~ult~ of thi~ testing by relating generated web width to pr~m~r prepar~tion.
SJUW ~ - ~IT-2D~ ~' OmW~
~ M~ Pd~c. ~ ~. ~I ~. I~I llo ~rl_r ph~rl~ l vol~-e.r 12 1~ 1/125/- 7~t ph~rl-~ pol~t r ~3 ~ 3~ 7~t ph~rl-~-d~. polrl~ld- 12 1~ 2 13 pb ~ ~ PTn 12 1~ --- 2 1~2 _t~l-~-d pol~ -t r 12 7~t --- 1~ 2 ehrl-~ ol~t-~ t 1 l~t --- 3/t 1 1/2 _ hrl-b- d polrldd-- 17 1 1/~ ___ 1/2 2 1/~
~thrl-b- d Pr~P 12 2 1 The slit-edge ~web~ generation data presented in Table III illu-Rtrate~ the primer performance of the 208~696 14 ~a~E~T~_ prlmers ln accordance wlth the present inventlon in the secure anchoring of phenyl-based silicone PSA'~ to different industriAl tape film substrate~. The primers are ffpecific in uoe for tha phenyl-basQd PSA's whereas thQ methyl-based primer i8 ~pecific for its use w~th methyl-based silicone PSA' 8 Fig. 1 further illustrate~ this specificity in use. Of the tested primer/adhe~ive combin~tionJ, the more thickly applied primer~ a~ prepared by #12 ~eyer rod show improvement in anchorage when compared to #8 Meyer rod prepared ~ample~.
Fig. 1 highlight~ primer re~ultJ for Ex~mple I
bacauoe thi~ variant diJplay~d a usQful, workable life after being catalyzed, ~b~th life~, sim11ar to the standard shown in Ex~mple III. Th- composition of E~ample II did not perform quite 80 well as that of Example I, and itJ bath life was shorter. The difficulty in proces~ibility of the Example II primer was probably due to the instability resulting from the exce~s cross-linker and thus the higher rate and degree of cross-linking.
Although the pre~ent invention hM~ been described in connection with preferred embodiments, it will be appreciated by those skilled in the art that addition~, modification~, substitutions and deletions not specifically de~cribed may be made without departing from tho spirit and scope of the invention defined in the appended claims.

Claims

1. A pressure sensitive adhesive tape comprising a substrate, a cured primer composition coated onto said substrate in the form of a primer layer, and a pressure sensitive adhesive layer coated onto said cured primer composition, said cured primer composition comprising a cross-linked phenyl-substituted siloxane gum, said pressure sensitive adhesive layer comprising a high molecular sensitive adhesive layer comprising functional organosiloxane polymer and a silanol-functional resin, said adhesive layer being at least partially cross-linked to said primer layer and securely anchored to said substrate.

2. A pressure sensitive adhesive tape according to claim 1, wherein said phenyl-substituted siloxane gum of said primer composition and said phenyl substituted silanol-functional organosiloxane polymer of said adhesive comprise diphenyl functional groups.

3. A pressure sensitive adhesive tape according to claim 2, wherein the total mole percent of phenyl substituents in each of said siloxane gum of said primer composition and said phenyl substituted silanol-functional organosiloxane polymer of said adhesive is between about 5.0 and about 5.5 mole percent.

4. A pressure sensitive adhesive tape according to claim 1, wherein said phenyl-substituted siloxane gum of said primer composition and said phenyl substituted silanol-functional organosiloxane polymer of said adhesive comprise diphenyl functional groups and dimethyl functional groups.

5. A pressure sensitive adhesive tape according to claim 4, wherein the total mole percent of phenyl substituents in each of said siloxane gum of said primer composition and said phenyl substituted silanol-functional organosiloxane polymer of said adhesive is between about 5.0 and about 5.5 mole percent.

6. A pressure sensitive adhesive tape according to claim 1, wherein said substrate comprises at least one member selected from the group consisting of polyester, polyimide and polytetrafluoroethylene.

7. A pressure sensitive adhesive tape according to claim 1, wherein said substrate has a thickness of between about one and two mils and said primer layer is applied to said substrate at a coverage of between about 0.2 and about 0.5 pounds per ream.

8. A pressure sensitive adhesive tape according to claim 1, wherein said cross-linking agent comprises methyl hydrogen fluid.

9. A pressure sensitive adhesive tape according to claim 8, wherein said cross-linking agent is present in an amount of about four percent by weight relative to the weight of the phenyl-substituted siloxane gum of said primer composition.

10. A pressure sensitive adhesive tape according to claim 1, wherein said siloxane gum of said primer composition has a molecular weight in the range of about 300,000 to about 600,000.

11. A pressure sensitive adhesive tape according to claim 1, wherein said siloxane gum of said primer composition has a total mole percent of phenyl substituents which is within ten percent the total mole percent of phenyl substituents in said phenyl substituted silanol-functional organosiloxane polymer of said adhesive.

12. A method of securely anchoring a phenyl-based pressure sensitive adhesive composition to a substrate, said method comprising:
applying a primer compsition to said substrate to form a primer layer on said substrate, said primer comprising a phenyl substituted siloxane gum and a cross-linking agent, dispersed in a solvent therefor;
curing said primer composition with a catalyst to form a cured primer layer on said substrate;
applying a phenyl-based pressure sensitive adhesive composition comprising a phenyl substituted silanol-functional organosiloxane polymer and a silanol-functional MQ resin, to said cured primer layer: and curing said phenyl-based pressure sensitive adhesive so as to cross-link said adhesive to said cured primer layer.

13. A method according to claim 12, wherein said phenyl-substituted siloxane gum of said primer composition and said phenyl substituted silanol-functional organosiloxane polymer of said adhesive comprise diphenyl functional groups.

14. A method according to claim 13, wherein the total mole percent of phenyl substituents in each of said siloxane gum of said primer and said phenyl substituted silanol-functional organosiloxane polymer of said adhesive is between about 5.0 and about 5.5 mole percent.

15. A method according to claim 12, wherein said phenyl-substituted siloxane gum of said primer composition and said phenyl substituted silanol-functional organosiloxane polymer of said adhesive comprise diphenyl functional groups and dimethyl functional groups.

16. A method according to claim 15, wherein the total mole percent of phenyl substituents in each of said siloxane gum of said primer composition and said phenyl substituted silanol-functional organosiloxane polymer of said adhesive is between about 5.0 and about 5.5 mole percent.

17. A method according to claim 12, wherein said primer composition is applied at a coverage of between about 0.2 and about 0.5 pounds per ream.

18. A method according to claim 17, wherein said primer composition is applied to said substrate with a #12 Meyer rod.

19. A method according to claim 17, wherein said primer composition is applied to said substrate with a #8 Meyer rod.

20. A method according to claim 12, wherein said phenyl-based pressure sensitive adhesive is cured by a solvent flash technique followed by a peroxide cure.

21. A method according to claim 12, wherein said siloxane gum of said primer composition has a total mole percent of phenyl substituents which is within ten percent the total mole percent of phenyl substituents in said phenyl substituted silanol-functional organosiloxane polymer of said adhesive.

22. A method according to claim 12, wherein said catalyst is a tin catalyst.

23. A primer coated substrate having a primed surface to which a phenyl-based pressure sensitive adhesive layer can adhere, said adhesive comprising a phenyl-substituted, organosiloxane polymer and a silanol-functional resin, said primer coated substrate comprising a substrate and a primer composition applied to said substrate to form a primer layer and said primed surface, said primer layer comprising phenyl substituted siloxane gum chains having silanol-functional end groups which have been cross-linked by a catalyzed silanol-hydride reaction.

24. A primer coated substrate according to claim 23, wherein said substrate has a thickness of between about one and two mils and said primer layer is applied to said substrate at a coverage of between about 0.2 and about 0.5 pounds per ream.

PATENTS

25. A primer coated substrate according to claim 23, wherein said siloxane gum of said primer composition has a molecular weight in the range of about 300,000 to about 600,000.

26. The invention as defined in any of the preceding claims including any further features of novelty disclosed.