JPH1160962A - Photosensitive resin composition for casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition, capable of manufacturing a duplicate model with a high dimensional accuracy by casting by simultaneously including a specific photopolymerization initiator, a leuco dye and a compound capable of generating an acid by irradiation of active rays. SOLUTION: This composition simultaneously contains (A) a photopolymerization initiator capable of generating free radicals by irradiation of active rays in an amount of 0.1-10 wt.% based on the total weight of the composition, (B) a leuco dye (e.g. 3-butyl-6-methyl-7-anilinofluorane) in an amount of 0.5-10 wt.% based on the total weight of the composition, (C) a compound capable of generating an acid by irradiation of the active rays (e.g. a cationic polymerization initiator) in an amount of 0.1-10 wt.% based on the total weight of the composition and preferably further (D) a polymer having ethylenically unsaturated bonds in the molecule and 800-9,000 molecular weight and (E) an ethylenically unsaturated compound having an ethylenically unsaturated bond and <800 molecular weight in an amount of >=50 wt.% based on the total weight of the composition. The composition can be used to provide a rigid and hardly breakable duplicate model in a short time by simple operations.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive resin composition for casting used for producing a duplicate model by casting.

[0002]

2. Description of the Related Art A small number of prototype models and small-scale production of duplicate models are obtained by taking a silicone rubber mold from a master model, injecting a thermosetting resin into the mold in a vacuum, and then heating and curing. Has been done in However, thermosetting resins are usually of two-part type, and the mixing of the two parts takes a short time until the start of curing. However, depending on the case, there is a problem in that curing may start during the pouring operation, resulting in a defective product.
Furthermore, the container used for mixing and casting must be washed each time before the resin is cured, which is troublesome. In addition, this method requires a long time of about two hours for heat curing, and requires one day. There was also a disadvantage that the number that could be copied was limited.

[0003] On the other hand, Japanese Patent Application Laid-Open No. 58-80587 discloses a method in which a one-part UV curable synthetic resin is injected into a transparent silicone rubber mold and irradiated with UV light under reduced pressure. A method of replicating a plastic watch case is shown. As a resin which is cured by ultraviolet rays, a resin obtained by adding benzophenone as a sensitizer to a synthetic resin for casting such as a spirane resin, or an unsaturated polyester resin containing a reaction accelerator is used.

Japanese Patent Application Laid-Open No. 3-114711 discloses a method of injecting a photosensitive resin into a transparent silicone rubber mold and curing the resin by irradiating ultraviolet rays, wherein a diacrylate of an ethylene oxide adduct of bisphenol A is used as the photosensitive resin. And a mixture of phenyl glycidyl ether and an acrylic acid ester to which a photopolymerization initiator is added.

Further, JP-A-7-124962 discloses a urethane poly (meth) acrylate having two or more (meth) acryloyloxy groups, a specific diallyl compound, and an aliphatic polythiol compound having two or more thiol groups. , An active energy ray-curable liquid resin composition obtained by adding an active energy ray polymerization initiator is injected into a transparent silicone rubber mold, and then irradiated with active energy rays to cure the resin molded article. Have been. Further, the present applicant has disclosed a photosensitive resin composition in which the disadvantage that the photosensitive resin is easily broken is improved as disclosed in
No. 244,044 and Japanese Patent Application Laid-Open No. 8-323778.

[0006] A high quality dimensional accuracy is required for a duplicate product obtained by casting, but the photosensitive resin shrinks when cured by ultraviolet rays, so that the size of the duplicate product obtained is smaller than that of the master model. There was a problem that it would be. Although it is possible to correct the shrinkage by making the master model large, it is inefficient to make a prototype model for initial shape evaluation and a master model for duplication separately, and the range of use is limited I had to become something.

It is desired that some of the replica models of the prototype be colored in an opaque color, such as milky white or black, depending on the application. However, in order to make the photosensitive resin opaque, for example, titanium oxide or carbon black is used. When added, it was difficult to color opaquely, for example, the sensitivity was lowered and the thickness that could be cured was limited. Coloring of the duplicates has been carried out, for example, by applying a coating treatment. However, in addition to an increase in the number of coating steps, there have been problems such as being unsightly when the coating is peeled off.

The present applicant has previously found that calcium carbonate is effective for coloring milky white.
No. 205467 and Japanese Patent Application No. 9-55444 which is an application based on this application. However, if a coloring agent is added to color it to some other color such as black, it is almost opaque, and almost no ultraviolet light is transmitted. Therefore, it is not possible to make a duplicate by light casting, and the duplicate is colored black. No cured photosensitive resin for casting has been practically used.

In order to inject the photosensitive resin composition into a silicone rubber mold and to irradiate and cure it with ultraviolet rays, an exposing machine having a vertically arranged light source as used in printing plate manufacturing is used. Exposure to light does not sufficiently cure the side surface of the model, resulting in a defective product. To make a mold with silicone rubber requires a long time of 10 hours or more to cure, so from the user's request to evaluate a replicated product within the shortest possible time after designing a model shape, There has also been a desire for use in combination with time-curable silicone rubber.

[0010]

SUMMARY OF THE INVENTION A method for producing a replica model by preparing a mold from an ultraviolet-permeable silicone rubber based on a master model, injecting a photosensitive resin composition into the mold and irradiating the mold with ultraviolet rays. In the photosensitivity, the replicated product is colored in an opaque color and can be cured with ultraviolet light even in a model with a large wall thickness, giving a replicated model with higher dimensional accuracy, and a replicated model that is hard and resistant to cracking It is an object to provide a resin composition, and also to provide a photosensitive resin composition for casting suitable for obtaining a duplicate product in a short period of time by a simple operation. It is.

[0011]

Means for Solving the Problems The present inventor has set forth the above object as an object of the present invention is to provide a photopolymerization initiator which generates free radicals by irradiation with actinic radiation in an amount of 0.1 to 10% by weight based on the total weight of the photosensitive resin composition. % Leuco dye 0.5 to 10% by weight It is found that the problem can be solved by using a photosensitive resin composition which simultaneously contains 0.1 to 10% by weight of a compound capable of generating an acid upon irradiation with actinic radiation. It was just.

Hereinafter, the present invention will be described in detail. Although the leuco dye itself used in the present invention is gray or nearly colorless, when the leuco dye is used in combination with a compound that generates an acid upon irradiation with ultraviolet light, the leuco dye is deeply colored by the acid generated after irradiation with ultraviolet light, and does not emit any light. It is possible to use a black color that does not pass. This is because a compound having the property of generating an acid by ultraviolet irradiation generates an acid rather than a photopolymerization initiator having a property of generating a free radical by ultraviolet irradiation and initiating polymerization, rather than generating a free radical. This is because, during the photocuring of the duplicated product by photopolymerization, the ultraviolet transmittance does not increase so much. After that, the leuco dye is sufficiently colored by continuously irradiating with ultraviolet rays or adding and irradiating after removing the duplicate and removing the duplicate, so that it is thick even when it is colored almost completely impermeable to black. It has the advantage that a cured product can be obtained.

As the leuco dye, 3-butylamino-
6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-xylidinofluoran,
3- (4-diethylamino-2-ethoxyphenyl)-
3- (1-ethyl-2-methylindol-3-yl)
-4-azaphthalide and the like can be mentioned as examples, but in view of the degree of black color, 3-butyl-6-methyl-
7-anilinofluoran is most preferred.

The leuco dye is usually added in the range of 0.5 to 10% by weight based on the total weight of the photosensitive resin composition. If the amount is too small, a sufficient color-forming effect cannot be obtained. If the amount is too large, the ultraviolet ray transmittance of the photosensitive resin composition becomes small due to its own ultraviolet absorption, so that the curable thickness becomes small. The preferred range is 1 to 6% by weight. Since the leuco dye often has poor solubility with other components of the photosensitive resin composition, it is preferable to add the leuco dye as finely as possible. Even if the leuco dye may separate and settle during storage of the photosensitive resin composition for casting, since it can be again dispersed uniformly by stirring before use, there is no practical problem. .

As the photopolymerization initiator which generates free radicals upon irradiation with actinic rays, a photopolymerization initiator capable of absorbing ultraviolet rays having a wavelength of 300 to 400 nm to generate free radicals and start polymerization is used. Is done. For example, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin-n-butyl ether, α-methylol benzoin methyl ether, α-methoxybenzoin methyl ether, benzoin derivatives such as α-ethoxybenzoin ethyl ether, 1-hydroxycyclohexylphenylacetophenone, 1-
Benzyl-1-dimethylaminopropyl-p-morpholinoketone and the like can be mentioned. Among them, α-methoxybenzoin methyl ether is particularly preferable because it can be cured to a material having a high curing rate and a large thickness.

The compounding amount of the photopolymerization initiator which generates free radicals upon irradiation with actinic radiation may be an effective amount for initiating polymerization.
It is used in the range of 0% by weight. If the amount is less than this, the photopolymerization initiation efficiency becomes poor, and in particular, the curing on the surface in contact with the silicone rubber becomes poor, and the adhesiveness may remain on the surface of the duplicate product, which is not preferable. Conversely, if the amount is too large, the mechanical properties of the cured product are undesirably reduced. The preferred range is 0.
The content is 5 to 4% by weight, and a more preferable range is 1 to 2.5% by weight.

As the compound which generates an acid upon irradiation with actinic radiation, a commercially available cationic polymerization initiator can be used, and is not particularly limited. Something like this,
BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , Sb
There are triarylsulfonium salts, diaryliodonium salts, aryldiazonium salts and the like having F _6- ^{and the} like. fluoroborate counterion is AsF ₆ ^- a is tris (methylphenyl) sulfonium salt, counterion AsF ₆ ^- a is diphenyl iodide salt and di-tolyl iodide salt, counterion BF ₄
^And- diphenyliodonium salt, ditolyliodonium salt, phenyldiazonium tetrafluoroborate, tolydiazonium tetrafluoroborate, and tolydiazonium hexafluorophosphate.

These act to generate an acid such as a Lewis acid or a Bronsted acid by the active irradiation to cause the leuco dye to develop color. Of these, triarylsulfonium salts are preferred from the viewpoint of the coloring effect. The amount of the compound that generates an acid upon activation irradiation is added in the range of 0.1 to 10% by weight based on the total weight of the photosensitive resin composition. The effect of forming the leuco dye is reduced, and if the amount is large, the ultraviolet absorption of the leuco dye itself is increased, and in some cases, the curing of the photosensitive resin composition and the coloring of the leuco dye occur simultaneously, thereby curing the photosensitive resin composition. There is a disadvantage that the possible thickness is reduced. From such a viewpoint, a preferable addition amount is 1 to 6% by weight.

If necessary, inorganic fillers may be added at the same time to ensure opacity even if the cured thickness is small, or to improve physical properties. Examples of the inorganic fillers include calcium carbonate, magnesium hydroxide, magnesium carbonate, and zinc oxide. Titanium oxide has a feature that it can be added only in a small amount because it has a large ultraviolet absorption, and that the resulting copy is gray because it has a large whitening effect. Therefore, it is not suitable for coloring in black, but may be added at the same time when coloring in gray is desired.

There is no particular limitation on the shape of the inorganic filler such as calcium carbonate as long as it can be dispersed in the photosensitive resin composition, and granular or fibrous materials can be used. In the case of granular materials, those having a particle size of 10 μm or less are usually used. If the particle size is large, it becomes easy to separate and settle during storage after being added to and mixed with the photosensitive resin composition.
Below, more preferably 2 μm or less is suitable. In the case of a fibrous material, a photosensitive resin composition for casting to which a resin having a thickness of 1 μm or less and a length of 5 μm or more has been added and mixed is preferably not easily separated and settled when stored for a long period of time. In this respect, those having a thickness of 0.2 μm or less and a length of 15 μm or more are more preferable.

From the viewpoint that inorganic fillers such as calcium carbonate hardly separate and settle during storage of the photosensitive resin composition for casting, fibrous ones are superior to spherical ones. Further, even when separated during storage, it can be used by stirring again. An inorganic filler such as calcium carbonate is added in a range of 3 to 20 parts by weight based on 100 parts by weight of the photosensitive resin composition so that the ultraviolet transmittance falls within a predetermined range. If the amount is less than this, sufficient opacity cannot be obtained, and if the amount is too large, the elongation at break of the duplicated product becomes small, so that it is not easy to be cracked and the thick part becomes difficult to harden, which is not preferable. It is more preferably in the range of 5 to 15 parts by weight.

As a method for obtaining the photosensitive resin composition for casting of the present invention by adding and mixing an inorganic filler to the photosensitive resin composition, an inorganic filler may be added to the photosensitive resin composition and stirred and dispersed. Alternatively, when the constituent components of the photosensitive resin composition are mixed, an inorganic additive may be added and stirred and mixed at the same time. At this time, heating may be performed to lower the viscosity of the photosensitive resin composition to facilitate mixing.

The inorganic additive hardly dissolves in the photosensitive resin composition and makes the photosensitive resin composition opaque because it reflects and scatters incident light. Calcium carbonate, magnesium carbonate, magnesium hydroxide, magnesium oxide, etc. also have a small absorption of ultraviolet light, so the scattered light is absorbed by the photoinitiator in the photosensitive resin composition and is used to start the curing reaction, so the thickness is large. Curing is possible even in a part, and the opaque and thick wall can satisfy the contradictory characteristics that curing is possible.

In particular, calcium carbonate has a great effect of completely opaque, and fibrous ones also have an effect of improving heat resistance. Therefore, calcium carbonate is most suitable as an inorganic filler used together in the photosensitive resin composition of the present invention. . The thickness of the duplicate model is usually 2 to 3 mm, but sometimes from 4 mm to 6 mm. The photosensitive resin composition for casting of the present invention can cure the thickness in this range.

Surprisingly, the photosensitive resin composition for casting of the present invention has the effect of improving the dimensional accuracy of a duplicate product produced using the same. This is because the difference in ultraviolet intensity between the light incident surface and the inside of the photosensitive resin composition for casting is large, so the difference in time required for each part to be cured is large, and the peripheral part is cured first. Since the resin that shrinks after curing shrinkage is replenished through the uncured center, the finished model will retain the original dimensions,
Such an effect is exhibited. The dimensions of the replica are required to be within ± 0.3% of the master model, which can be achieved by the method of the present invention.

In the present invention, the composition of the photosensitive resin composition used as the photosensitive resin for casting, which simultaneously contains a photopolymerization initiator leuco dye which generates free radicals upon irradiation with actinic rays and a compound which generates an acid upon irradiation with actinic rays. Although there is no particular restriction on the molecular weight, considering the balance with other properties such as hardness and resistance to cracking required for producing a replicated product, the molecular weight having an ethylenically unsaturated bond in the molecule is 80%.
It is preferable to use a photosensitive resin composition comprising a polymer having a molecular weight of 0 to 9000 and an ethylenically unsaturated compound having a molecular weight of less than 800 as an essential component.

Examples of the polymer having a molecular weight of 800 to 9000 having an ethylenically unsaturated bond in the molecule include unsaturated polyurethane and unsaturated polyester. From the viewpoint of the balance between hardness and resistance to cracking, unsaturated polyurethane is more preferable. The unsaturated polyester is obtained by a dehydration condensation reaction between a diol compound and a dicarboxylic acid compound having at least one kind having an unsaturated bond. The unsaturated polyurethane is obtained by reacting a diol compound and a diisocyanate compound, and then reacting a compound having an ethylenically unsaturated bond with a hydroxyl group or an amino group or a compound having an ethylenically unsaturated bond with an isocyanate group.

In a method of first synthesizing a polyurethane polymer having isocyanate groups at both terminals and reacting it with a compound having both a hydroxyl group and an ethylenically unsaturated bond, a compound having both a hydroxyl group and an ethylenically unsaturated bond is used. In order to facilitate the reaction with the polyurethane polymer having an isocyanate group and to terminate the reaction in a short time by suppressing side reactions, the reaction is performed by adding the number of hydroxyl groups to the number of isocyanate groups in excess. Is preferred. Usually, an excess of about 2 to 5 times is added. The result is a mixture of a polyurethane polymer having ethylenically unsaturated bonds and an excess of hydroxyl-containing ethylenically unsaturated compounds.

In a method of first synthesizing a polyurethane polymer having hydroxyl groups at both ends and reacting it with a compound having both an isocyanate group and an ethylenically unsaturated bond, the compound having both an isocyanate group and an ethylenically unsaturated bond is a polyurethane polymer. It is generally added in the same or less range as the number of hydroxyl groups of the polymer, but in this case, in order to facilitate stirring and suppress side reactions,
It is preferable to reduce the viscosity of the reaction system by using a component not involved in the urethanization reaction as a diluent. When a compound having both an isocyanate group and an ethylenically unsaturated bond is added in excess, it is necessary to eliminate the isocyanate group by adding a compound having an active hydrogen such as a hydroxyl group after completion of the reaction.

As the diol compound, compounds having two hydroxyl groups in one molecule, for example, polyester glycol such as polypropylene glycol adipate diol, polyneopentyl glycol adipate diol, polycaprolactone diol, polyvalerolactone diol, polyethylene glycol, polypropylene Examples thereof include polyether diols such as glycol and polytetramethylene glycol. The molecular weight of the diol compound is usually about 400 to 2,000, but from the viewpoint of obtaining a stronger one,
It is preferable to use one having a molecular weight of about 100 to 1,000.

Examples of the diisocyanate compound include compounds having two isocyanate groups, for example, tolylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate and the like. Among these, tolylene diisocyanate is preferable because it does not increase the viscosity so much and a hard and tough product is easily obtained.

Examples of the compound having both a hydroxyl group and an ethylenically unsaturated group include hydroxyethyl methacrylate and acrylate, hydroxypropyl methacrylate and acrylate, N-methylolacrylamide, polyoxyethylene glycol monomethacrylate, polyoxypropylene glycol monomethacrylate, and the like. It can be mentioned as. Among these, hydroxyethyl methacrylate and hydroxypropyl methacrylate are preferred from the viewpoint of hardness and toughness, and hydroxypropyl methacrylate from which higher hardness is obtained is most preferred. As a compound having both an isocyanate group and an ethylenically unsaturated group, for example, a compound obtained by adding a diisocyanate compound one-to-one to a compound having a hydroxyl group and an ethylenically unsaturated group at the same time can be mentioned.

The unsaturated polyurethane obtained as described above preferably has a number average molecular weight of 800 to 9000 determined by GPC measurement using polystyrene as a standard. Although having the advantage that the viscosity of the obtained photosensitive resin composition can be lowered as the molecular weight is smaller, when the molecular weight is smaller than this, the cured product becomes hard and brittle and loses toughness, and when cutting and removing unnecessary portions of a duplicated product, It is not preferable because cracks easily occur. If the molecular weight is large, the toughness of the cured product is easy to secure, but if it is larger than this, the viscosity of the obtained photosensitive resin composition increases, making it difficult to spread the photosensitive resin to every corner of the mold in the casting process In addition to the above, there are unfavorable aspects of the properties of the duplicated product, such as softening of the obtained cured product.

Examples of the ethylenically unsaturated compound having a molecular weight of less than 800 include N-methylolacrylamide, diacetoneacrylamide, N, N-dimethylacrylamide,
N-substituted acrylamides such as N- (2-methoxyethyl) acrylamide, N-methylol methacrylamide, N, N-dimethylmethacrylamide, N-substituted methacrylamides, hydroxy such as hydroxyethyl methacrylate and acrylate, hydroxypropyl methacrylate and acrylate Alkyl methacrylates and acrylates, ethylene glycol dimethacrylate and acrylates, diethylene glycol dimethacrylate and diacrylate, tetraethylene glycol dimethacrylate and diacrylate such as polyoxyethylene glycol dimethacrylate and diacrylate,

Polyoxypropylene glycol dimethacrylate and diacrylate such as propylene glycol dimethacrylate and diacrylate, dipropylene glycol dimethacrylate and diacrylate, tripropylene glycol dimethacrylate and diacrylate, butanediol dimethacrylate and diacrylate, hexanediol Examples thereof include dimethacrylate and diacrylate, nonanediol dimethacrylate and diacrylate, trimethylolpropane trimethacrylate and triacrylate, and diacrylate and dimethacrylate having a bisphenol A skeleton.

Among these, N-methylolacrylamide and methacrylamide are preferred from the viewpoint of increasing hardness and heat resistance without significantly lowering toughness. From the viewpoint of increasing toughness without significantly lowering hardness and heat resistance. Diacetone acrylamide is preferred. Further, from the viewpoint of lowering the viscosity of the photosensitive resin composition and increasing the elongation properties and hardness, etc., hydroxyethyl methacrylate, hydroxypropyl methacrylate, trimethylolpropane trimethacrylate, etc., while further maintaining toughness From the viewpoint of increasing hardness and heat resistance, diacrylate and dimethacrylate having a bisphenol A skeleton are suitable. Usually, these are used in combination.

Usually, an ethylenically unsaturated compound having a molecular weight of less than 800 is used in an amount of 60 to 200 parts by weight based on 100 parts by weight of a polymer having an ethylenically unsaturated bond in the molecule and having a molecular weight of 800 to 9000. Further, the total amount of both is preferably at least 50% by weight in the photosensitive resin composition, preferably at least 70% by weight, more preferably at least 80% by weight. If the amounts are small, a cured product having sufficient physical properties cannot be obtained. In addition, a stabilizer such as a known thermal polymerization inhibitor can be added in order to ensure the stability during production or storage of the photosensitive resin composition. Examples of such stabilizers include p-methoxyphenol, 2,6-di-t-butyl-p-cresol, and the like.

The viscosity of the photosensitive resin composition at 20 ° C. is preferably 300 P or less, more preferably 200 P or less, in order to make it easy for bubbles mixed in during the work to escape and to spread to every corner of the silicone rubber mold. Is 150P
It is desirable that: The viscosity of the photosensitive resin composition can be reduced by increasing the blending ratio of the ethylenically unsaturated compound, particularly the liquid ethylenically unsaturated compound. Among the liquid ethylenically unsaturated compounds, those having a small molecular weight are particularly effective in lowering the viscosity. It is also effective to reduce the viscosity by adding a liquid plasticizer such as silicone oil in a range that does not significantly affect other properties.

When the viscosity of the photosensitive resin composition for casting is high, the viscosity during use can be lowered by increasing the temperature of the photosensitive resin composition at the time of casting. Must be used in a temperature range in which this does not occur because it may cause deterioration.

The silicone rubber used as the mold in the present invention may be of any type as long as it has a property of transmitting ultraviolet light. Usually, a commercially available room temperature-curable (RTV) transparent silicone rubber is used. Either a transparent silicone rubber or an ultraviolet-curable type can be used as long as it is capable of transmitting ultraviolet rays to the extent necessary for curing the photosensitive resin composition for casting. Room temperature curing type (RTV)
Transparent silicone rubber is a two-part composition, which is complicated to handle and requires one night to cure, whereas an ultraviolet-curing type is usually easy to handle with one part and can be cured in a short time of about 10 to 20 minutes. It is also suitable from the viewpoint of creating a mold in a short time.

Silicone rubbers are classified according to the curing mechanism into addition type and condensation type. The condensation type is preferable in terms of dimensional accuracy because the low molecular weight compound generated during condensation shrinks when it goes out of the system. However, an additional type without such a thing is suitable. By using the photosensitive resin composition for casting of the present invention, a product having a high dimensional accuracy of 0.3% or less can be obtained. If the temperature is lower than the temperature at which the silicone rubber is cured to form the mold, the temperature of the silicone rubber mold at the time of injecting the photosensitive resin composition for casting into the mold and irradiating with ultraviolet light to cure is used. It is also effective to increase the temperature up to 50 ° C.

Since the thermal expansion of the silicone rubber is several steps larger than that of the photosensitive resin composition for casting, the photosensitive resin composition for casting hardens while the silicone rubber mold is swollen beyond the size of the master model. On the other hand, the cured photosensitive resin for casting has a small shrinkage due to a temperature difference even when the temperature is lowered, so that the shrinkage during curing is corrected, and a duplicate having better dimensional accuracy can be obtained.

The point that it is easy to keep the curing temperature constant is 2
In general, the silicone rubber is cured at 5 to 40 ° C., and the temperature of the silicone rubber mold is desirably 80 ° C. or less in consideration of the ease of handling of the silicone rubber mold during the casting operation. In addition, if the temperature difference between the silicone rubber at the time of mold production and casting is too large, the size of the duplicate product obtained will be larger than the master model and may worsen, so it is necessary to keep the temperature difference within an appropriate range. There is.

The light source used for photocuring is 300 to 400.
Anything that emits ultraviolet light having a wavelength of nm may be used, and an ultraviolet fluorescent lamp, a high-pressure mercury lamp, a metal halide lamp, a xenon lamp, or the like that is usually used for curing a photosensitive resin can be used.

Unlike the production of a printing plate or the baking of a resist, the production of a duplicate model requires that ultraviolet rays be irradiated from the top, bottom, left, right, front and rear directions during photocuring, and is used for that purpose. It is desirable that the light sources are arranged in six directions, that is, up, down, left, right, front and rear. Although the number of light source arrangements can be reduced by using a reflector, it is necessary to determine the shape and arrangement of the reflectors so that light is emitted from six directions even in such a case. If light irradiation is performed only from the same vertical direction as that for preparing the printing plate, the portion corresponding to the side surface is insufficiently cured, resulting in a defective product, which is not preferable. In order to cure a large-sized object, it is preferable to perform exposure while moving the inside of a light source arranged in a cylindrical exposure machine in which light sources are arranged vertically and horizontally or a conveyer or the like.

[0046]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0047]

【Example】

Example 1 100 g of a diol diacrylate obtained by adding a total of 4 moles of ethylene oxide to bisphenol A, 50 g of a diacrylate obtained by adding 2-hydroxyethyl acrylate to both ends of hexamethylene diisocyanate, and 6 g of α-methoxybenzoin methyl ether were mixed. Using the obtained photosensitive resin composition, a three-dimensional three-dimensional molding process was performed for 20 hours. The outer dimensions were 5 cm in height, 5 cm in width, and 4 in height.
cm, 3 mm thick as a master model, in the center of a box 13 cm wide, 13 cm deep and 13 cm high, prepared by assembling a 10 mm thick transparent polymethyl methacrylate resin plate containing no UV absorber I set it.

25 ° C., both ends blocked with hydroxy groups
5000 cP dimethylpolysiloxane 1
000 g, fumed silica 100 g, methacryloxypropyltrimethoxysilane 17 g, tin dioctoate 1
Photocuring obtained by mixing 0 g, 30 g of 2-ethylhexyl propionate 2-trimethoxysilyl, 50 g of a mercapto group-containing organopolysiloxane represented by the following formula (1), 20 g of diethoxyacetophenone and 5 g of dibutyltin dilaurate. Water-soluble silicone rubber composition

[0049]

Embedded image (Where n is an integer that gives a viscosity of 35 cP at 25 ° C.)

The mixture was poured into the box and placed in an exposing machine in which 40 W ultraviolet fluorescent lamps having a central wavelength of 370 nm were arranged in six directions, up, down, left, right and front, and irradiated with ultraviolet rays for 20 minutes. After exposure, the silicone rubber cured product was cut out to remove the master, and the inside of the mold was additionally exposed for 5 minutes in the same exposure machine to obtain a casting mold.

680 g of polycaprolactone diol having an average molecular weight of 500 determined from the hydroxyl value, and polypropylene glycol 450 having an average molecular weight of 950 determined from the hydroxyl value.
g and tolylene diisocyanate (371 g) were reacted to obtain a polyurethane having isocyanate groups at both ends.
Further, 345 g of 2-hydroxypropyl methacrylate was added and reacted to obtain an unsaturated polyurethane having a chain-extended urethane bond and having a number average molecular weight in terms of polystyrene of 5,800 as measured by GPC.

The above unsaturated polyurethane (excess 2-hydroxypropyl methacrylate 1 as a diluent monomer)
116 g, 2-hydroxypropyl methacrylate 91 g, diacetone diacrylamide 25 g,
2.6 g of α-methoxybenzoin methyl ether, 2,
0.2 g of 6-di-t-butyl-p-cresol, 11 g of leuco dye 3-dibutylamino-6-methyl-7-anilinofluoran, photoacid generator triarylsulfonium hexafluorophosphate (manufactured by Sartomer Co., Ltd. 11 g of a trade name CD-1011) was mixed to obtain a photosensitive resin composition for casting having a viscosity of 60 P at 20 ° C.

The photosensitive resin composition for casting was degassed under reduced pressure at 40 ° C., and then poured into the silicone rubber mold.
A 10 mm thick UV-free polymethyl methacrylate plate (Delaglass K, color number 3002 manufactured by Asahi Kasei Kogyo Co., Ltd., color number 3002) is applied to the top and bottom of the silicone rubber mold and fixed with transparent tape, and placed in the above exposure machine for 10 minutes. Ultraviolet irradiation was performed. Thereafter, the mold was opened and a duplicate made of the cured photosensitive resin was taken out. This replica was slightly dark gray, but turned into completely black after an additional 10 minutes of additional exposure.
The Shore D hardness of this duplicate was 82 degrees. Table 1 shows the measurement results of the dimensions at each location. The resin injection port portion of this duplicate was cut with a nipper, but no crack was generated.

Example 2 Using a master sheet made of ABS having a thickness of 6 mm, a length of 50 mm and a width of 20 mm, and using a transparent silicone rubber KE-1606 (manufactured by Shin-Etsu Chemical Co., Ltd.) of a room temperature curing type which was previously defoamed under vacuum. And cured at 40 ° C. to produce a casting mold.

Poly-1,4-butylene glycol adipate diol 300 having a molecular weight of 510 determined from the hydroxyl value
g, also polypropylene glycol 5 having a molecular weight of 960
2.5 g and 173 g of tolylene diisocyanate were reacted to obtain a polymer having isocyanate groups at both ends. Then 2-hydroxypropyl methacrylate 30
3 g (of which 202 g is excess addition as diluent monomer)
Was added to react with the isocyanate group of the polymer to obtain a urethane prepolymer having a number average molecular weight of 2,300 as determined by GPC using polystyrene having methacrylate groups at both ends as a standard.

124 g of this prepolymer (24 g of 2-hydroxypropyl methacrylate as diluent monomer)
), 2-hydroxypropyl methacrylate 26
g, 7 g of tetraethylene glycol dimethacrylate,
15 g of a reaction product of propylene oxide adduct of bisphenol A and glycidyl methacrylate (trade name 3002M, manufactured by Kyoeisha Yushi Co., Ltd.), 2,2-dimethoxy-2-
Phenylacetophenone 3g, leuco dye 3-diethylamino-6-methyl-7-anilinofluoran 5.16
g, photoacid generator triarylsulfonium hexafluorophosphate (trade name: CD-101, manufactured by Sartomer Co., Ltd.)
1) 8 g was mixed to obtain a photosensitive resin composition for casting having a viscosity of 85P at 20 ° C.

The above-described photosensitive resin composition for casting, which was previously heated to 40 ° C. and defoamed, was poured into the transparent silicone rubber mold heated to 65 ° C. under reduced pressure. After returning to normal pressure, a 10-mm-thick polymethyl methacrylate plate without a UV absorber was fixed to the upper and lower sides of the silicone rubber mold in the same manner as in Example 1, and exposed for 10 minutes in the same manner as in Example 1. went. Thereafter, the duplicated product made of the cured photosensitive resin was taken out and subjected to additional exposure for 10 minutes. As a result, a completely black replica having a thickness of 6 mm was obtained. The resin injection port of this duplicate was cut off with a nipper, but no crack was generated in the duplicate.

Example 3 A duplicated product was prepared in the same manner as in Example 2 except that the same photosensitive resin composition for casting was used, the exposure time was 25 minutes, and no additional exposure after demolding was performed. As a result, a copy having completely black color was obtained.

[0059]

[Table 1]

[0060]

By using the photosensitive resin composition for casting of the present invention, it is possible to obtain an opaque, black, thick replica with high dimensional accuracy. Further, a hardened and hard-to-break duplicate model can be produced in a defect-free form.

Claims (2)

[Claims] 1. A photopolymerization initiator which generates free radicals by irradiation with actinic radiation, 0.1 to 10% by weight, a leuco dye, 0.5 to 10% by weight, based on the total weight of the photosensitive resin composition. A photosensitive resin composition for casting, which comprises 0.1 to 10% by weight of a compound capable of generating an acid. 2. A polymer having an ethylenically unsaturated bond in the molecule and having a molecular weight of 800 to 9000. An ethylenically unsaturated compound having a molecular weight of less than 800 having an ethylenically unsaturated bond is added to the photosensitive resin composition based on the total weight of the photosensitive resin composition. The photosensitive resin composition for casting according to claim 1, which is contained in an amount of 50% by weight or more.