United States Patent [19J
`Shiobara et al.
`
`[54] LIGHT TRANSMISSIVE EPOXY RESIN
`COMPOSmONS AND OPTICAL
`SEMICONDUCfOR DEVICES
`ENCAPSULATED THEREWITH
`
`[75]
`
`Inventors: Tosbio Sbiobara; Koji Futatsumori;
`Kazuhiro Arai, all of Annaka, Japan
`
`[73] Assignee: Sbin-Etsu Chemical Company
`Limited, Tokyo, Japan
`
`[21] Appl. No.: 749,379
`
`[22] Filed:
`
`Aug. 23, 1991
`
`Related U.S. Application Data
`[63] Continuation-in-part of Ser. No. 651,438, Feb. 7, 1991.
`
`Foreign Application Priority Data
`[30]
`Aug. 24, 1990 [JP]
`Japan .................................. 2-223052
`
`Int. CJ,S ................................................ C08K 9/06
`-(51]
`[52] U.S. Cl •.................................... 523/214; 523/219;
`523/444
`[58] Field of Search ........................ 523/214, 219, 444
`
`lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll
`US005198479A
`5,198,479
`[11] Patent Number:
`[45] Date of Patent: Mar. 30, 1993
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`4,842,837 6/1989 Shimizu et a! ...................... 423/335
`4,985,751 1/1991 Shiobara eta! ....................... 357/72
`
`OTHER PUBLICATIONS
`Best, M. F., Condrate, R. A. Sr.; "A Raman Study of
`Ti02-Si02 Glasses Prepared by Sol-Gel Processes";
`Journal of Materials Science Letters, 4, 1985, 994-998.
`Primary Examiner-Paul R. Michl
`Assistant Examiner-V. K. Rajguru
`Attorney, Agent, or Firm-Millen, White, Zelano and
`Branigan
`ABSTRACf
`[57]
`In a light transmissive epoxy resin composition com(cid:173)
`prising (A) an epoxy resin and (B) a curing agent are
`blended (C) an organic phosphorus anti-discoloring
`agent and (D) silica-titania glass beads surface treated
`with an organic silicon compound. The composition
`restrains coloring in composition form and discolor(cid:173)
`ation in cured form while curing into clear low stressed
`products having high light transmittance. Optical semi(cid:173)
`conductor devices encapsulated with the cured epoxy
`resin composition are reliable.
`
`9 Claims, 1 Drawing Sheet
`
`4
`
`I
`
`5
`
`5
`
`Vizio EX1017 Page 0001
`
`

`
`U.S. Patent
`U.S. Patent
`
`Mar. 30, 1993
`Mar. 30, 1993
`
`5,198,479
`5,198,479
`
`FIG.1
`
`4
`
`
`
`5
`
`5
`
`Vizio EX1017 Page 0002
`
`Vizio EX1017 Page 0002
`
`

`
`1
`
`5,198,479
`
`LIGHT TRANSMISSIVE EPOXY RESIN
`COMPOSmONS AND OPTICAL
`SEMICONDUCTOR DEVICES ENCAPSULATED
`THEREWITH
`
`2
`gel, followed by grinding and firing of the dry gel. By
`changing the mix proportion of silicon alkoxide and
`titanium alkoxide, silica-titania glass beads can be con(cid:173)
`trolled to a desired refractive index, that is, match with
`5 the refractive index of cured epoxy resins.
`It was expected that by blending such silica-titania
`glass beads in epoxy resin compositions as a filler, there
`would be obtained epoxy resin cured products high
`transparency, a low coefficient of linear expansion, and
`low stress.
`In attempts to blend silica-titania glass beads in epoxy
`resin compositions along with organic phosphorus anti(cid:173)
`discoloring agents which were found to be most effec-
`tive in preventing the epoxy resin compositions from
`discoloring upon high-temperature treatment, it was
`found that the interaction between the organic phos-
`phorus anti-discoloring agent and silica-titania glass
`beads gave rise to yellowing phenomena. Unlike the
`above-mentioned browning of cured products upon
`high-temperature treatment, serious color development
`occurred even at room temperature as long as both the
`components co-existed, resulting in a substantial lower(cid:173)
`ing of light transmittance of the cured products.
`The filled epoxy resin compositions also suffered
`from the problem that the cured products became tur(cid:173)
`bid and low in light transmittance due to light scattering
`caused by separation and gaps occurring at the interface
`between the resin component and the filler.
`Therefore, a mere combination of an organic phos-
`phorus anti-discoloring agent with silica-titania glass
`beads failed to provide a light transmissive epoxy resin
`capable of meeting all the requirements of anti-discolor(cid:173)
`ing upon high-temperature treatment, high transpar-
`ency, and low coefficient of linear expansion. The fllled
`epoxy resin compositions as such were impractical for
`semiconductor encapsulating purposes.
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`This application is a continuation-in-part of copend(cid:173)
`ing application Ser. No. 07/651,438, flied Feb. 7, 1991 10
`pending ..
`This invention relates to a light transmissive epoxy
`resin composition suitable for encapsulating optical
`semiconductor devices such as LED, CCD, and photo(cid:173)
`couplers. It also relates to an optical semiconductor 15
`device encapsulated with the epoxy resin composition
`in cured state.
`
`25
`
`BACKGROUND OF THE INVENTION
`Epoxy resins are well known in the art to have im- 20
`proved electrical properties, humidity resistance and
`heat resistance. Among others, epoxy resin composi(cid:173)
`tions of the acid anhydride curing type are widely used
`in encapsulating optical semiconductor devices because
`of their light transparency.
`Often anti-discoloring agents are added to such light
`transmissive epoxy resin compositions in order to pre(cid:173)
`vent them from changing their color toward brown
`upon high-temperature treatment into cured products.
`The known anti-discoloring agents are organic phos- 30
`phorus compounds, hindered phenols and thioethers.
`The inventors have found that the organic phosphorus
`anti-discoloring agents are most effective among these
`agents.
`It is also a common practice to produce low stressed 35
`epoxy resins compositions by blending inorganic filler
`such as silica therein, thereby reducing a coefficient of
`linear expansion.
`Epoxy resin compositions having inorganic flllers
`such as silica loaded therein, however, cure to opaque 40
`products although both the epoxy resin and filler com(cid:173)
`ponents are transparent. This is because most cured
`epoxy resins have a refractive index (n25 D) of about 1.5
`to 1. 7 and its difference from the refractive index of
`filler (for example, N25 v::::: 1.458 for Si02 causes light 45
`scattering. This suggests that if a filler having a refrac(cid:173)
`tive index approximate to that of cured epoxy resins
`were blended, cured products would be transparent.
`In this regard, the inventors found that silica-titania
`glass having a high refractive index is an effective inor- 50
`ganic filler. In general, sol-gel methods are known for
`preparing transparent glass species having varying in(cid:173)
`dexes of refraction. The sol-gel methods produce glass
`by starting with a solution of organic and inorganic
`compounds of metals, causing hydrolysis and polymeri- 55
`zation of the compounds in the solution to form a sol
`having fine particles of metal oxide or hydroxide sus(cid:173)
`pended, causing the reaction to proceed further to con(cid:173)
`vert the sol into a gel, and heating the porous gel into an
`amorphous glass or polycrystalline body. The inventors 60
`previously proposed a method for preparing high trans(cid:173)
`parency silica-titania glass beads in the above-referred
`application Ser. No. 07/651,438. This method produces
`silica-titania glass beads by furnishing a mixed solution
`of metal alkoxides (silicon alkoxide and titanium alkox- 65
`ide), alcohol and water, gradually evaporating alcohol
`from the solution, causing hydrolysis and polyconden(cid:173)
`sation to form a sol and then a wet gel, and drying the
`
`SUMMARY OF THE INVENTION
`We have found that by treating silica-titania glass
`beads on their surface with an organic silicon com(cid:173)
`pound and blending the surface treated beads along
`with an organic phosphorus anti-discoloring agent in a
`light transmissive epoxy resin composition comprising a
`compound having at least two epoxy groups in a mole(cid:173)
`cule, an acid anhydride curing agent, and a curing pro(cid:173)
`moter, there is obtained a light transmissive epoxy resin
`composition which can not only restrain the color de(cid:173)
`velopment due to the interaction between silica-titania
`glass beads and the organic phosphorus anti-discoloring
`agent, but also enhance the interfacial adhesion between
`the resin component and the flller beads and which
`cures to transparent, low stressed products while pre(cid:173)
`venting any discoloration upon high-temperature treat(cid:173)
`ment. Consequently, optical semiconductor devices
`encapsulated with such epoxy resin compositions a
`cured state can perform their function to a greater ex(cid:173)
`tent than the devices encapsulated with prior art light
`transmissive epoxy resin compositions.
`Therefore, the present invention provides a light
`transmissive epoxy resin composition comprising
`(A) a compound having at least two epoxy groups in
`a molecule,
`(B) an acid anhydride curing agent,
`(C) an organic phosphorus anti-discoloring agent,
`and
`(D) silica-titania glass beads surface treated with an
`organic silicon compound.
`
`Vizio EX1017 Page 0003
`
`

`
`5,198,479
`
`3
`An optical semiconductor device encapsulated with a
`cured product of the light transmissive epoxy resin
`composition is also contemplated.
`
`BRIEF DESCRIPTION OF THE ORA WING
`The only FIGURE, FIG. 1 is a schematic cross-sec(cid:173)
`tional elevation of a photo-coupler used in Example 15.
`
`20
`
`4
`to 10 parts, especially 1 to 6 parts by weight per 100
`parts by weight of components (A) and (B) combined.
`Component (D) is silica-titania glass beads surface
`treated with an organic silicon compound. The silica-
`s titania glass beads should preferably have a linear trans(cid:173)
`mittance of at least 70%, especially at least 80% as
`measured at a wavelength in the range of from 900 nm
`to 600 nm by a linear transmittance measurement
`method A.
`10 Method A involves the steps of mixing a bisphenol
`type epoxy resin of the general formula (1) shown
`below or a novolak type epoxy resin of the general
`formula (2) shown below with phenylglycidyl ether to
`form a solution having a difference in refractive index
`15 from the silica-titania glass beads within ±0.002; mixing
`the solution with the silica-titania glass beads which
`have been ground to a mean particle diameter of 5 to 30
`JLm in a weight ratio of 1:1; and measuring the linear
`transmittance of the mixture across a light path length
`of 1 mm.
`Formula (1):
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`Component (A) of the light transmissive epoxy resin
`composition of the invention is a compound having at
`least two epoxy groups per molecule. It may be selected
`from conventional well-known epoxy resins which may
`be either liquid or solid. Illustrative examples include
`epoxy resins synthesized from epichlorohydrin and
`bisphenols including various novolak resins, cycloali(cid:173)
`phatic epoxy resins, and epoxy resins having halogen
`atoms such as chlorine and bromine atoms incorporated
`therein, alone or in admixture of two or more.
`.Preferred are least colored bisphenol type epoxy
`resins which are commercially available as Epikote 828,
`Epikote 1001, and Epikote 1004 (trade name, Yuka
`Shell Epoxy K.K.), RE 310S andRE 304S (trade name,
`Nihon Kayaku K.K.), and DER 332, DER 661 and
`DER 664 (trade name, Dow Chemical Co.).
`Component (B) is an acid anhydride ·curing agent
`which may be selected from well-known ones com(cid:173)
`monly used for epoxy resins. Examples of the curing 30
`agent include phthalic anhydride, trimellitic anhydride,
`.
`and pyromellitic anhydride, with aromatic ring-free
`anhydrides such as hexahydrophthalic anhydride and
`tetrahydrophthalic anhydride being preferred.
`In the practice of the invention, a curing promoter 35
`may be blended for the purpose of promoting reaction
`between epoxy resin (A) and curing agent (B), if de(cid:173)
`sired. Examples of the curing promoter include imidaz(cid:173)
`ole
`and
`its
`derivatives
`such
`as
`2-ethyl-4-
`methylimidazole, 2-phenylimidazole, and 1-cyanoethyl- 40
`2-methylimidazole; tertiary amine derivatives such as
`1 ,8-diaza-bicyclo(5.4.0)-undecene-7 and benzyl-dime(cid:173)
`thylamine; and phosphine derivatives such as triphenyl
`phosphine and nonyl diphenyl phosphine. It will be
`appreciated that acid anhydride curing agent (B) and 45
`In formulae (1) and (2), a is an integer of from 0 to 10.
`the optional curing promoter may be added in com-
`Such highly transparent silica-titania glass beads can
`monly used amounts. Preferably, component (B) is 10 to
`be prepared by the sol-gel method disclosed in the
`100 parts by weight per 100 parts by weight of compo-
`above-referred
`copending
`application Ser. No.
`nent (A). The curing promoter, if any, is up to 10 parts
`especially 0.1 to 10 parts by weight per 100 parts by 50 07/651,438 as comprising the steps of hydrolyzing and
`polycondensing a silicon alkoxide and a titanium alkox-
`weight of components (A) and (B) combined.
`A light transmissive epoxy resin composition of com-
`ide to form a silica-titania sol, causing the silica-titania
`ponent (A), component (B) and an optional curing pro-
`sol to gel, drying the gel, grinding the dry gel to a pre-
`mater all as defmed above is further blended with (C) an
`determined particle size, and thereafter heating the
`organic phosphorous anti-discoloring agent and (D) 55 ground gel at a temperature of 1,050 to 1,250• C. into a
`silica-titania glass beads surface treated with an organic
`sintered glass.
`silicon compound in order to provide a light transmis-
`More particularly, the source materials used herein
`sive epoxy resin composition of the invention. As a
`are silicon alkoxides such as Si(OCH3)4 and Si(OC2Hs)4
`result of blending components (C) and (D), the compo-
`and titanium alkoxides such as Ti(OC3H7)4 and Ti-
`sition cures to low stressed products capable of main- 60 (OC4B9)4. The silicon and titanium alkoxides are prefer-
`taining high transparency in a stable manner.
`ably mixed such that Ti02may range from 10 to 18 mol
`The organic phosphorus anti-discoloring agents (C) % of the total of Si02 and Ti02 in the fmal product.
`include triphenyl phosphite, tridecyl phosphite, di-
`Silica-titania glass beads with a Ti02 content ofless than
`10 mol% will sometimes have a refractive index below
`phenylmonodecyl phosphite, 9,10-dihydro-9-oxa-10-
`phosphaphenanthrene-10-oxide, 10-decyloxy-9,10-dihy- 65 the minimum level of 1.53 acceptable as the epoxy resin
`filler. Silica-titania glass beads with a Ti02 content of
`dro-9-oxa-10-phosphaphenanthrene, etc. alone and mix-
`tures of two or more. The amount of the organic phos-
`more than 18 mol % will often have a too high refrac-
`phorus anti-discoloring agent blended is preferably 0.1
`tive index to find a matching transparent epoxy resin.
`
`25
`
`Formula (2):
`
`(I)
`
`(2)
`
`Vizio EX1017 Page 0004
`
`

`
`5,198,479
`
`6
`
`(3)
`
`5
`The sol or gel is obtained from these source materials
`by dissolving the silicon and titanium alkoxides in a
`diluting solvent in the form of an alcohol such as metha(cid:173)
`nol, ethanol, and propanol. Water is added to the solu(cid:173)
`tion to form a silica-titania sol through hydrolysis. The 5
`sol is then poured into a gelling vessel which is closed.
`The vessel is placed stationary in a constant tempera(cid:173)
`ture dryer where the sol is converted into gel. The
`temperature during this gelation and subsequent aging
`should preferably be 60° C. or higher because hydroly- 10
`sis of alkoxides cannot proceed to completion below 60°
`C., leaving the likelihood of generating trivalent Ti ions
`which can cause coloring during subsequent sintering
`step. Since the aging is intended for completing the
`hydrolysis, the aging time is preferably at least one 15
`hour, more preferably at least 5 hours.
`The wet gel resulting from gelation and aging is then
`dried by any desired method, for example, by removing
`the lid from the gelling vessel and keeping the vessel
`open along with the gel contents in the constant temper- 20
`ature dryer until the gel is dry.
`Then the dry gel is ground prior to sintering. That is,
`the dry gel is ground by conventional methods using
`ball mills or the like to an appropriate particle size, often
`an average particle size offrom I to 100 ILm, preferably 25
`from 5 to 30 ILm·
`The finely divided dry gel is then heated or fired into
`sintered glass at a sintering temperature in the range of
`from 1,050° C. to 1,250° C. At temperature of lower
`than 1,050° C., the silica-titania glass beads are not fully 30
`uniformly consolidated and show low transmittance
`values as when light is directed to the beads for measur(cid:173)
`ing the transmittance thereof, the light is scattered
`within the bead interior due to differential refraction at
`cracks or interstices in the beads. If the sintering tern- 35
`perature rxceeds 1,250° C., the anatase phase, which is
`one of crystalline phases of TiOz, appears, preventing
`the formation of silica-titania glass beads having high
`light transmission.
`Insofar as the sintering temperature falls within the 40
`above-defined range, the remaining parameters of the
`sintering step are not particularly limited. Preferably,
`electric furnaces or similar firing furnaces which can
`maintain a constant temperature are used while oxygen
`gas or a mixture of oxygen and air is introduced into the 45
`furnace to establish an oxidizing atmosphere therein
`effective for preventing the generation of trivalent Ti
`ions which will otherwise cause coloring. The furnace
`is typically heated at a rate of 10° to 500° C./hour until
`the predetermined temperature is reached. The heating 50
`or sintering time is usually 10 to 300 minutes in the
`above-defined temperature range.
`The silica-titania glass beads should have a refractive
`index approximate to the refractive index of cured resin
`so that the light scattering associated with the silica- 55
`titania glass beads in the epoxy resin may be minimized.
`Desirably, the difference in refractive index should be
`within ±0.01, more desirably within ±0.005, most
`desirably within ±0.002.
`In the present invention, the silica-titania glass beads 60
`on the surface are treated with an organic silicon com(cid:173)
`pound.
`The organic silicon compounds used herein are typi(cid:173)
`cally silane coupling agents, silanes, and organopolysi(cid:173)
`loxanes as shown below. One or more of these com- 65
`pounds may be used for surface treatment.
`Organosilanes having the following general formula
`(3):
`
`to 5
`wherein R 1 represents an alkyl group having
`carbon atoms, R2 represents an alkyl group having 1 to
`12 carbon atoms or an aryl group having 6 to 10 carbon
`atoms and 1 is an integer of 1 to 4.
`Examples of the organosilanes of formula (3) are
`shown below.
`Si(OCH3)4, Si(OCH2CH3)4, CH3Si(OCH3)3,
`
`CH3(CH2)nCH2Si(OCH3)3 (n= 1 to 10), etc.
`Organosilanes (silane coupling agents) having the
`following general formula (4):
`
`(4)
`
`wherein X represents an organic group containing at
`least one group selected from the group consisting of an
`epoxy group, an amino group, a carboxyl group, a hy(cid:173)
`droxy group, a mercapto group, a ureido group, a
`maleimido group and trialkoxysilyl groups and having 0
`to 10 carbon atoms, R3 and R4 independently represent
`a monovalent hydrocarbon group having 1 to 6 carbon
`atoms such as an alkyl group, an alkenyl group and an
`aryl group, p is an integer of 1 to 12, and q is an integer
`of 1 to 3.
`Examples of the silane coupling agents of formula (4)
`are shown below.
`
`CH2-CHCH20C3H6Si(OCH3)3,
`\
`I
`0
`
`CH3
`I
`CH2-CHCH20(CH2)3Si(OC=CH2)3,
`\
`I
`0
`
`CH3
`I
`CH2-CHCH20(CH2)3Si(OCH3h.
`\
`I
`0
`
`CH2-CH-CH2(CH2)nCH2Si(OCH3)3,
`\
`I
`0
`
`NH2C3H6Si(OCH3)3, NH2C2l4NHC3H6Si(OCH3)3,
`
`HSCJH6Si(OCHJ)3,
`
`Vizio EX1017 Page 0005
`
`

`
`5,198,479
`
`7
`-continued
`
`0
`II
`NH2CNHC3H6Si(OCH3)3,
`
`0
`
`II c NC,H,Si(OCH,,
`
`~
`0
`
`Organopolysiloxanes having the following
`formula (5):
`
`Rl
`I
`YOi"SiOt,;Y
`i2
`
`general
`
`(5)
`
`20
`
`25
`
`30
`
`8
`pound diluted with a solvent through a spray or the like,
`and operating the mixer to effect mixing and agitation.
`Also the wet method may be a conventional one
`involving the steps of mixing a filler, organic silicon
`5 compound, and solvent, agitating the mixture, and then
`removing the solvent. Any desired solvent may be used
`although a selected solvent such as toluene, methyl
`ethyl ketone, and methyl isobutyl ketone is preferred
`since the solvent dictates the adsorption of the organic
`10 silicon compound to the filler. It is also effective to heat
`at 100• to 600• C. after solvent removal.
`The coverage of an organic silicon compound on
`silica-titania glass beads is determinable in accordance
`with the amount of the same organic silicon compound
`15 blended relative to an ordinary flller which is given by
`the following formula.
`Amount of organic silicon compound blended
`(g)= [filler weight (g)+ filler BET specific surface area
`(m2fg)]/[minimum coverage area (m2fg)].
`The minimum coverage area is the theoretically pos-
`sible area of the filler that a unit weight of the organic
`silicon compound can cover. For a trialkoxy CF silane,
`if all the alkoxy groups in a molecule were subject to
`hydrolysis and attached to the filler surface, the cover-
`age area is the area of an imaginary circle that could
`pass the three attachments. For a dialkoxy CF silane,
`the coverage area is the area of a similar imaginary
`circle that could have a diameter between the two at-
`tachments. The minimum coverage area is the total area
`(cm2) of these circles that 1 gram of each CF silane can
`cover. Since each different CF silane has its own molec(cid:173)
`ular weight, it has a specific minimum coverage area.
`In one exemplary embodiment, 0.1 to 2 parts, prefera-
`35 bly 0.6 to 1.2 parts by weight of an organic silicon com(cid:173)
`pound is used per 100 parts by weight of silica-titania
`glass beads.
`The silica-titania glass beads surface treated with an
`organic silicon compound in this way is blended in an
`40 amount of about 10 to about 600 parts, more preferably
`about 50 to about 300 parts by weight per 100 parts by
`weight of components (A) and (B) combined. Less than
`10 parts of the glass beads would not always provide a
`low shrinkage factor and low expansion whereas more
`45 than 600 parts of the glass beads would sometimes result
`in too viscous a composition.
`In addition to the above-mentioned essential compo(cid:173)
`nents (A) to (D), any conventional well-known curing
`promoters, stress lowering agents, mold release agents,
`50 visible light shielding agents, flame retardants and other
`additives may be blended in the composition of the
`present invention, if necessary, insofar as they do not
`detract from transparency.
`The light transparent epoxy. resin composition of the
`55 invention is prepared by uniformly milling the neces(cid:173)
`sary components in mixing means such as, for example,
`mixers, kneaders, roll mills, and extruders. The order of
`blending the components is not particularly limited.
`Regardless of the nature of the resinous components,
`the compositions of the invention are advantageously
`applicable to the encapsulation of optical semiconduc(cid:173)
`tor devices which function to emit and receive light
`signals, for example, LED, CCD, and photo-couplers.
`Where the compositions are liquid at room temperature,
`suitable molding techniques are potting and casting.
`Transfer molding and injection molding techniques are
`suitable for solid compositions at room temperature.
`They are generally molded at a temperature of from so·
`
`wherein Y represents a hydrogen atom or an alkyl
`group having 1 to 5 carbon atoms, n is an integer of 1 to
`10, and Rl and R2 are as defined above. Examples
`thereof are shown below.
`
`HO
`
`fi-0
`
`H, CH30
`
`CH3
`
`n
`
`ii-0
`
`CH3
`
`CH3
`
`n
`
`-rt -rt
`~ ~, t
`~ ~, t
`
`HO
`
`Si-0
`I
`CH3
`
`fi-0
`
`H,
`
`CH3
`
`y
`
`CH30
`
`Si-0
`I
`CH3
`
`fi-0
`
`CH3
`
`CH3
`
`X
`
`y
`
`In the formulae, xis an integer of 1 to 9, y is an integer
`of 1 to 9, and x+y;§ 10.
`It will be appreciated that the organic silicon com(cid:173)
`pounds having a refractive index approximate to that of
`silica-titania glass beads are preferred for further im- 60
`proving the transparency of cured products.
`Silica-titania glass beads are surface treated with such
`an organic silicon compound by either a dry or a wet
`method. The dry method may use well-known means.
`One exemplary conventional dry method is by placing a 65
`filler (beads) in a high speed mixer capable of high speed
`rotation with increased shearing forces and having a
`heater built therein, adding an organic silicon com-
`
`Vizio EX1017 Page 0006
`
`

`
`5,198,479
`
`9
`to 160• C., and post cured at a temperature offrom 140•
`to 160• C. for 2 to 16 hours.
`Where some or all the components of the curable
`epoxy resin composition are solid, it is advantageous to
`heat melt at least some of such solid components prior 5
`to mixing. Alternatively, a solid component(s) is dis(cid:173)
`solved in a solvent and uniformly mixed with the re(cid:173)
`maining components before the solvent is stripped off.
`There have been described light transmissive epoxy
`resin compositions comprising a light transmissive 10
`epoxy resin compound and an organic phosphorus anti(cid:173)
`discoloring agent and a filler in the form of silica-titania
`glass beads surface treated with an organic silicon com(cid:173)
`pound loaded therein. This combination is not only
`effective in deterring any color development that can 15
`occur due to the interaction between the anti-discolor(cid:173)
`ing agent and the filler, but the anti-discoloring agent
`can also exert its own function of inhibiting any discol(cid:173)
`oration due to oxidative degradation upon heat treat(cid:173)
`ment into cured products. By virtue of the inclusion of 20
`well transparent silica-titania glass particles, the light
`transmitting epoxy resin compositions of the invention
`provide cured ones characterized by high transparency,
`a low shrinkage factor, a low coefficient of thermal
`expansion, and low stress. The compositions are very
`useful in encapsulating optical semiconductor devices
`and allow the optical semiconductor devices encapsu(cid:173)
`lated therewith to exert their optical function to a full
`- extent and be reliable.
`
`25
`
`30
`
`10
`Treatment (c)
`Silica-titania glass beads (a) resulting from Treatment
`(a) were allowed to stand in an electric oven at 600• C.
`for one hour, obtaining silica-titania glass beads (c)
`surface treated with an organic silicon compound.
`
`Treatment (d)
`Silica-titania glass beads (b) resulting from Treatment
`(b) were allowed to stand in an electric oven at 600• C.
`for one hour, obtaining silica-titania glass beads (d)
`surface treated with an organic silicon compound.
`The organic silicon compounds used are shown be(cid:173)
`low.
`KBM 403 is 'Y-glycidoxypropyltrimethoxysilane of
`the formula:
`
`KBM 103 is phenyltrimethoxysilane of the formula:
`
`and KBM 04 is tetramethoxysilane of the formula:
`
`EXAMPLE
`Examples of the present invention are given below by
`way of illustration and not by way of limitation. All
`parts are by wight.
`First, we will show how to prepare the silica-titania
`glass beads surface treated with an organic· silicon com(cid:173)
`pound used in Examples and Comparative Examples.
`
`35
`
`all available from Shin-Etsu Chemical Co, Ltd.
`- There were used two types of silica-titania glass
`beads having different indexes of refraction and differ(cid:173)
`ent Ti02 contents, that is, silica-titania glass beads I for
`liquid compositions having n25 D= 1.5430 and silica(cid:173)
`titania glass beads II for solid compositions having
`n25 D= 1.5706, such that the difference in index of re(cid:173)
`fraction was within ±0.0005 relative to the resinous
`compound ofliquid and solid compositions of Examples
`and Comparative Examples. ·
`Table 1 reports the data of these two types of silica(cid:173)
`titania glass beads I and II with respect to index of
`refraction, transmittance and particle size distribution.
`TABLE 1
`
`40
`
`PREPARATION EXAMPLE
`A 1-liter four-necked flask equipped with a reflux
`condenser, thermometer, stirrer, ester adaptor and
`dropping funnel was charged with 200 grams of silica(cid:173)
`titania glass beads which were prepared in accordance
`with the Example of .the above-referred Ser. No. 45
`07/651,438 having a mean particle size of 10 ~J-m and 500
`grams of toluene. With stirring at the reflux tempera-
`ture, water was azeotroped off for one hour. To the
`Silica-
`Silica-
`flask, a mixture of 2 grams of an organic silicon com-
`titania
`titania
`t!:S\1
`~: 1
`pound selected from three types, KBM 403, KBM 103 50
`--------':':"'" ___ :.:..;. __ =;:;.;;;;-
`and KBM 04 (identified below), 0.02 grams ofDBU and
`I 5430
`Index of refraction n25 D
`1.5706
`87.9
`85:3
`20 grams of toluene was added dropwise over 5 min-
`at 700 nm
`Light
`83.1
`at 589 nm
`84.8
`utes. Stirring was continued for a further 4 hours at the
`transmittance,
`67.8
`68.0
`reflux temperature. Thereafter, the reaction mixture
`at 500 nm
`%
`was subjected to each of the following treatments (a) to 55 ___ ...;;M..:.ea:.;.;..n.::;P::•rt..::i::cl.:..e ::siz::e:..:., ,::1Lm::... __ .....;.IO..:..o:.... __ .....;.9..:..3:___
`(d).
`
`Treatment (a)
`By distilling off the solvent in vacuum from the reac(cid:173)
`tion mixture, there were obtained silica-titania glass 60
`beads (a) surface treated with an organic silicon com(cid:173)
`pound.
`
`The treatment methods involved are described be(cid:173)
`low.
`
`Measurement of Index of Refraction
`Abbe's refractometer 3T manufactured by Atago K.
`K. was used.
`
`Treatment (b)
`By removing the excess solvent from the reaction 65
`mixture by filtration and drying the residue at 120• C.,
`there were obtained silica-titania glass beads (b) surface
`treated with an organic silicon compound.
`
`Measurement of Light Transmittance
`Epikote 828 (epoxy resin available for Yuka Shell
`Epoxy K.K.) and phenylglycidyl ether were mixed in a
`controlled proportion to form a mixture (immersion
`solution) having a refractive index which differed
`
`Vizio EX1017 Page 0007
`
`

`
`11
`within ±0.002 from the refractive index of the silica(cid:173)
`titania (Ti02-Si02) glass beads as calculated from the
`Ti02 content. The solution was mixed with the silica(cid:173)
`titania glass beads having a mean particle diameter of 5
`to 30 /LID in a weight ratio of 1: 1. After the beads were 5
`fully dispersed, the mixture was deaerated in vacuum
`until no bubbles were visually observed. A cell having
`a light path length of 1 mm was charged with the mix(cid:173)
`ture which was measured for transmission spectrum 10
`over a wavelength range of from 900 nm to 400 nm by
`means of a spectrometer. The reference used was a
`blank.
`For silica-titania glass beads I and II, mixtures having
`a refractive index n25D of 1.5428 and 1.5705 were re(cid:173)
`spectively prepared and used and the immersion solu-
`tion.
`
`5,198,479
`
`12
`three light transmissive epoxy resin compositions which
`were solid at room temperature.
`
`COMPARATIVE EXAMPLE 3
`A light transmissive epoxy resin composition which
`was solid at room temperature was obtained by repeat(cid:173)
`ing the procedure of Example 3 except that 2 parts of
`triphenyl phosphite was omitted.
`
`COMPARATIVE EXAMPLE 4
`A light transmissive epoxy resin composition which
`was solid at room temperature was obtained by repeat(cid:173)
`ing the procedure of Example 3 except that 100 parts of
`15 silica-titania glass beads II was omitted.
`These epoxy resin compositions were molded and
`post cured into specimens under the conditions reported
`in Table 2.
`
`Measurement of Particle Size Distribution
`Using an aqueous solution containing 0.2% by weight
`of sodium hexametaphosphate as a dispersion medium
`for a simple, the particle size distribution was measured
`by means of a centrifugal settling machine, Model SA-
`CP3L (manufactured by Shimazu Mfg. K.K.).
`
`20
`
`25
`
`TABLE 2
`
`Moldins
`
`Pres-
`sure
`
`Time
`
`4
`hours
`
`Tern-
`per a-
`ture
`100' c.
`
`Post-
`curins
`
`Tern-
`pera-
`ture
`150' c.
`
`Time
`
`4
`hours
`
`Example I, 2
`Comparative
`EXAMPLES 1-2 AND COMPARATIVE
`Example I
`EXAMPLE 1
`150' c.
`150' c.
`4
`70
`Example 3, 4
`kglcm2
`hours
`min.
`Comparative
`A resinous compound was obtained by blending 53.1
`parts of bisphenol-A type epoxy resin I (trade name 30 ==.:..:....:,;__:, _______________ _
`Example 2, 3, 4
`Epikote 828, epoxy equivalent 190, liquid at room tem(cid:173)
`perature, available from Yuka Shell Epoxy K.K.), 46.9
`parts of methylhexahydrophthalic anhydride (trade
`name Rikacid MH-700, liquid at room temperature, 35
`available from Shin-Nihon Rika K.K.), 1 part of2-ethyl-
`4-m