Patent Application
20150338618
The present invention relates to a wafer lens, a molding die for a wafer lens, and a method of producing a wafer lens.
As a method of producing an imaging lens for an imaging device mounted on mobile terminals in a large amount at low cost, as shown in PTL 1, a known method is configured to produce an imaging lens as follows. That is, a hardenable resin material is coated on a substrate (or on a die), and the hardenable resin material is molded and hardened so as to form a wafer lens. Subsequently, the wafer lens is cut separately into individual lens pieces.
A wafer lens is formed such that multiple small lenses are arranged side by side on a single substrate with a large diameter. Now, description is given briefly to an example of a process of producing the wafer lens. First, a molding die is prepared so as to include a number of molding transferring surfaces and to have a size correspond to the substrate of the wafer lens, such as six inches or eight inches. Then, a hardenable resin material is held and sandwiched between the molding die and the substrate, and the hardenable resin material is hardened by being applied with heat or light. Thereafter, the hardened resin material is released from the molding die, whereby the wafer lens is obtained. To this wafer lens, an antireflection coat and the like are applied if needed, and the wafer lens is cut into individual lenses, whereby a large number of imaging lenses can be obtained by few processes.
PTL 1: U.S. Pat. No. 4,420,141
PTL 2: Japanese Unexamined Patent Publication No. 2008-310213
Incidentally, in a wafer lens which includes several tens to thousands of lens portions on the same wafer, administration of quality (optical surface configuration, wafer eccentricity, eccentricity between wafers) is important. At the time of molding, at the time of assessment, and at the time of stacking, in order to perform positioning with high precision, it becomes necessary to use an alignment mark portion with such a role. As a method for forming an alignment mark portion, PTL 2 discloses a technique to mold an alignment mark portion with a resin material as with a lens portion.
However, PTL 2 relates to a micro lens array, and in order to form the alignment mark portion, a resin material is coated on the entire surface of a molding die. On the other hand, since a wafer lens is produced for the purpose of mass-producing imaging lenses eventually, it becomes usually necessary to cut the produced wafer lens for each lens portion into individual pieces. Therefore, if a resin material is coated on the entire surface of a molding die of a wafer lens by diversion of the technique of PTL 2, since adjoining lens portions are connected to each other, a phenomenon that lens portions break at a cutting process may happen easily. As a method for avoiding this problem, it is considered not to connect adjoining lens portions with resin. As a method for realizing this, a separately-dropping molding method is effective. In this method, in order to prevent a resin material from spreading over on the entire surface of a glass substrate, the resin material is separately dropped by using a discharging apparatus, such as nozzles so as to dispose droplets individually for each lens portion and to mold them.
On the other hand, the alignment mark portion is requested to be recognized as a mark to perform positioning correctly. Further, in order to produce a wafer lens with a number of lens portions, it is also required to make the position of the alignment mark portion to be recognized easily. Therefore, in the case of forming an alignment mark portion by a resin material, since the alignment mark portion is needed to be shaped in a configuration with sufficient visibility, it is necessary to make the configuration different from that of a lens portion. However, in the case of forming the alignment mark portion by the resin material together with the lens portion, if the configuration of the alignment mark portion is different from that of a lens portion, at the time of dropping the resin material separately, it is necessary to drop the resin material individually in the respective amounts different in accordance with the respective configurations of them. As mentioned above, since a number of lens portions are formed on a wafer lens, the size of each lens portion is small and an arrangement distance between lens portions is also small. Accordingly, if the feeding amount of the resin material is changed only for the alignment mark portion, the resin material may adhere to the neighboring lens portion, or the amount of the resin material may become insufficient. Therefore, there is a fear that it may become difficult to produce an appropriate alignment mark portion.
Further, in the production of a wafer lens with the purpose of mass-producing imaging lenses at low cost, there are request to reduce the number of processes as small as possible and to shorten a tact time (cycle time). However, at the time of producing a lens portion and an alignment mark portion by separately-dropping of a resin material, if a dropping amount of the resin material is changed for each time, there are problems that adjustment and molding time are increased, for example, a trial operation is needed to stabilize a dropping amount of a discharging device (to drop the resin material to a location other than a substrate by trial), and a molding routine work is needed to be changed.
Furthermore, in PTL 2, since the resin material is printed on an alignment mark forming section of a molding die at a process other than an optical surface forming process, there is a fear that a positioning error between processes may occur and it may become difficult to secure the desired visibility of an alignment mark. In addition, there is also a problem that the number of processes increases with a process of printing an alignment mark forming section and a conveying process, which results in an increase of a production cost.
The present invention has been achieved in view of the above situations, and an object of the present invention is to provide a wafer lens with sufficient accuracy in which multiple lens portions and alignment mark portions are formed on a substrate, a molding die to mold this wafer lens, and a method of producing a wafer lens.
A wafer lens described in claim 1 includes a substrate and a resin-molded body which is formed with a distance on at least one surface of the substrate and is composed of a hardenable resin material; wherein the resin-molded body includes a lens portion and at least two alignment mark portions, the lens portion includes an optical surface and a lens annular portion formed at a periphery of the optical surface, and the alignment mark portion includes a flat surface portion on which an alignment mark is formed and a mark annular portion formed at a periphery of the flat surface portion, and wherein a volume at an inside of the lens annular portion of the lens portion is made substantially equal to a volume at an inside of the mark annular portion of the alignment mark portion.
According to the present invention, a volume at an inside of the lens annular portion of the lens portion is made substantially equal to a volume at an inside of the mark annular portion of the alignment mark portion. Accordingly, when a resin material is supplied between the substrate and the molding die by a separately-dropping method, it is permissible to supply a given amount of the resin material. Therefore, it becomes possible to avoid the following problems. When the resin material is supplied too much, a large quantity of the resin material overflows from the cavity of the molding die to mold the alignment mark portion, and the overflowing resin material connects with the neighboring lens portions, which causes cracks at the time of cutting a wafer lens. On the other hand, when the resin material is supplied too small, the alignment mark portion AM cannot be formed with sufficient accuracy. Here, the matter that a volume at an inside of the lens annular portion of the lens portion is made substantially equal to a volume at an inside of the mark annular portion of the alignment mark portion, means that a difference between the two volumes is within ±3%.
In the wafer lens described in claim 2 in the invention described in claim 1, the flat surface portion on which the alignment mark is formed has an outer diameter of 0.14 to 2 mm.
When the flat surface portion on which the alignment mark is formed has an outer diameter of 0.14 mm or more, a difference in area between the flat surface portion and the alignment mark is easily secured widely. Accordingly, when observing with a microscope or a camera, it becomes easy to recognize the alignment mark. On the other hand, when the flat surface portion on which the alignment mark is formed has an outer diameter of 0.2 mm or less, it is desirable, because the mark annular portion can be secured in a proper configuration.
In the wafer lens described in claim 3 in the invention described in claim 1 or 2, the alignment mark is constituted by at least one of a circle, an arc, and a straight line.
When the alignment mark is shaped into a circle configuration, there is an advantage that it is easy to make a transfer surface to transfer it by a machining process. Further, since it can be positioned with sufficient accuracy irrespective of the measuring direction, it is suitable to use it for measurement of an eccentricity in a wafer. Further, when stacking multiple wafers, if an inner diameter is changed, at the time of looking the alignment mark of a rear side wafer superimposed on the alignment mark of a front side wafer, it is desirable, because the alignment mark of a front side wafer does not become obstructive. In this case, it is preferable to make the area of the flat surface portion of the alignment mark at a front side larger than the area of the flat surface portion of the alignment mark at a rear side. On the other hand, when the alignment mark is formed by a line, there is an advantage that it is easy to make a transfer surface to transfer it by a machining process. Further, a line (which includes a cross shape in which lines are orthogonal to each other) allows to measure edges at several points and to obtain an average of the measurements, whereby an error can be eliminated and positioning can be performed with high precision. Accordingly, especially at the time of molding a wafer lens, it is suitable to use it to measure eccentricity between wafers at the time of stacking wafer layers.
In the wafer lens described in claim 4 in the invention described in any one of claims 1 to 3, the diameter of the lens annular portion at a position most distant from the substrate is made equal to the diameter of the mark annular portion at a position most distant from the substrate.
With this, the resin-molded body in which the lens portion and the alignment mark portion coexist together can be arranged easily with equal pitch on the substrate.
In the wafer lens described in claim 5 in the invention described in any one of claims 1 to 4, on a cross sectional surface of the resin-molded body in the optical axis direction passing through the optical axis of the lens portion, the outer shape of the lens annular portion is made substantially the same as the outer shape of the mark annular portion.
With this, the spreading of the resin material at the time of the separately-dropping becomes almost equal in the lens portion and in the alignment mark portion. Accordingly, dispersion in the dropping and the molding decreases, and it becomes easy to keep the quality at constant.
In the wafer lens described in claim 6 in the invention described in any one of claims 1 to 5, in the resin-molded body, the lens portion and the alignment mark portion are arranged with an equal pitch.
The resin-molded body is arranged with a shortened distance on the substrate, whereby the number of the resin-molded bodies per a single substrate is increased so as to enhance a yield.
Further, the resin material is dropped while shifting a dispenser to coat the resin material at an equal speed relatively to the substrate, whereby the supply of the resin material with an equal distance can be realized easily, which is effective for control of a supply amount of a resin material with high accuracy.
In the wafer lens described in claim 7 in the invention described in any one of claims 1 to 6, the lens portions are formed on both sides (i.e., both surfaces) of the substrate, and one of the alignment mark portions is used for positioning at the time of forming the lenses on the both sides of the substrate.
With this, at the time of forming the lenses on the both sides of the substrate, the respective optical axes of the two lens portions can be made coincide with each other with sufficient accuracy.
In the wafer lens described in claim 8 in the invention described in any one of claims 1 to 7, one of the alignment mark portions is used to detect a pitch error of the resin-molded bodies.
With this, whether the pitch of the lens portions is formed with sufficient accuracy can be judged. Accordingly, occurrence of defective products can be suppressed.
In the wafer lens described in claim 9 in the invention described in any one of claims 1 to 8, at the time of stacking multiple wafer lenses in the form of one on top of another, one of the alignment mark portions is used for positioning of the wafer lenses to be stacked.
With this, the respective optical axes of the lens portions disposed in the stacked wafer lenses can be made coincide with each other at once with sufficient accuracy.
A wafer lens molding die described in claim 10 is a wafer lens molding die which is arranged to face at least one surface of a substrate and is configured to form a resin-molded body including a lens portion and at least two alignment mark portions by sandwiching a hardenable resin material with the substrate therebetween. The wafer lens molding die comprises a lens cavity for forming the lens portion and a mark cavity for forming the alignment mark portion, wherein the lens cavity includes an optical surface forming section for forming an optical surface of the lens portion and a lens annular portion forming section for forming a lens annular portion around the optical surface, and the mark cavity includes a flat surface portion forming section for forming a flat surface portion of the alignment mark portion and a mark annular portion forming section for forming a mark annular portion around the flat surface portion, and wherein the volume of the lens cavity and the volume of the mark cavity are made substantially equal to each other.
According to the present invention, the volume of the lens cavity and the volume of the mark cavity are made substantially equal to each other. Accordingly, when a resin material is supplied between the substrate and the molding die by a separately-dropping method, it is permissible to supply a given amount of the resin material. Therefore, it becomes possible to avoid the following problems. When the resin material is supplied too much, a large quantity of the resin material overflows from the cavity of the molding die to mold the alignment mark portion, and the overflowing resin material connects with the neighboring lens portions, which causes cracks at the time of cutting a wafer lens. On the other hand, when the resin material is supplied too small, the alignment mark portion AM cannot be formed with sufficient accuracy. Here, the matter that the volume of the lens cavity and the volume of the mark cavity are made substantially equal to each other, means that a difference between the two volumes is within ±3%.
In the wafer lens molding die described in claim 11 in the invention described in claim 10, the flat surface portion forming section has an outer diameter of 0.14 to 2 mm.
When the flat surface portion forming section has an outer diameter of 0.14 mm or more, a difference in area between the flat surface portion formed by the flat surface portion forming section and the alignment mark is easily secured widely. Accordingly, when observing with a microscope or a camera, it becomes easy to recognize the alignment mark. On the other hand, when the flat surface portion forming section has an outer diameter of 0.2 mm or less, it is desirable, because the mark annular portion formed by the mark annular portion forming section can be secured in a proper configuration.
In the wafer lens molding die described in claim 12 in the invention described in claim 10 or 11, on the flat surface portion forming section, a concave potion or a convex portion each constituted by at least one of a circle, an arc, and a straight line, is disposed, and the alignment mark is formed by transferring the concave potion or the convex portion.
When the alignment mark is shaped into a circle configuration, there is an advantage that it is easy to make a transfer surface to transfer it by a machining process. Further, since it can be positioned with sufficient accuracy irrespective of the measuring direction, it is suitable to use it for measurement of an eccentricity in a wafer. On the other hand, when the alignment mark is formed by a line, there is an advantage that it is easy to make a transfer surface to transfer it by a machining process. Further, a line (which includes a cross shape in which lines are orthogonal to each other) allows to measure edges at several points and to obtain an average of the measurements, whereby an error can be eliminated and positioning can be performed with high precision. Accordingly, especially at the time of molding a wafer lens, it is suitable to use it to measure eccentricity between wafers at the time of stacking wafer layers.
In the wafer lens molding die described in claim 13 in the invention described in any one of claims 10 to 12, the concave portion or the convex portion is processed immediately after the mark cavity has been processed.
With this, since the center of the mark cavity and the center of the concave portion, or the convex portion are made coincide with each other with sufficient accuracy, it becomes possible to enhance the positional accuracy of an alignment mark formed by being transferred. Further, since the concave portion, or the convex portion is processed on the flat surface portion, an alignment mark with high precision and high reproducibility is created.
In the wafer lens molding die described in claim 14 in the invention described in any one of claims 10 to 13, the diameter of the lens annular portion forming section at the deepest position is made equal to the diameter of the mark annular portion forming section at the deepest position.
With this, the resin-molded body in which the lens portion and the alignment mark portion coexist together can be arranged easily with equal pitch on the substrate.
In the wafer lens molding die described in claim 15 in the invention described in any one of claims 10 to 14, when taking a cross sectional surface, the outer shape of the lens annular portion forming section is made substantially the same as the outer shape of the mark annular portion forming section.
With this, when molding a resin material supplied at the time of the separately-dropping, the spreading of the resin material becomes almost equal in the lens annular portion formed by the lens annular portion forming section and in the mark annular portion formed by the mark annular portion forming section. Accordingly, dispersion in the dropping and the molding decreases, and it becomes easy to keep the quality at constant.
In the wafer lens molding die described in claim 16 in the invention described in any one of claims 10 to 15, a distance between neighboring lens cavities is made equal to a distance between the neighboring lens cavity and the mark cavity.
A distance between neighboring lens cavities is made equal to a distance between the neighboring lens cavity and the mark cavity, whereby these cavities are arranged with a shortened distance, the number of the resin-molded bodies per a single substrate is increased so as to enhance a yield. Further, the resin material is dropped while shifting a dispenser to coat the resin material at an equal speed relatively to the substrate, whereby the supply of the resin material with an equal distance can be realized easily, which is effective for control of a supply amount of a resin material with high accuracy.
In the wafer lens molding die described in claim 17 in the invention described in any one of claims 10 to 16, the molding die includes a resin-made molding transferring surface obtained by being transferred from the master die.
With this, by molding only the master die serving as a single die, an accurate molding die can be easily duplicated.
In a wafer lens producing method described in claim 18 is a producing method of producing a wafer lens by using the molding die described in any one of claims 10 to 17, includes a process of supplying a hardenable resin material separately between the substrate and each of the lens cavity and the mark cavity, and a process of detecting a pitch error of a resin-molded body formed on the substrate by using an alignment mark portion formed by the mark cavity.
According to the present invention, the wafer lens producing method includes a process of detecting a pitch error of a resin-molded body formed on the substrate by using an alignment mark portion formed by the mark cavity. By detecting the alignment mark, whether the pitch of the lens portions is formed with sufficient accuracy can be judged. Accordingly, occurrence of defective products can be suppressed.
In a wafer lens producing method described in claim 19 is a producing method of producing a wafer lens by using a pair of the molding dies described in any one of claims 10 to 17, includes a process of supplying a first hardenable resin material separately between one surface of the substrate and each of the lens cavity and the mark cavity of one of the molding dies; a process of positioning anther one of the molding dies on another surface of the substrate by using an alignment mark portion formed by the mark cavity; and a process of supplying a second hardenable resin material separately between another surface of the substrate and each of the lens cavity and the mark cavity of another one of the molding dies.
According to the present invention, at the time of forming lens portions on the both sides of the substrate, the respective optical axes of the both lens portions can be made coincide with each other at once with sufficient accuracy.
In a wafer lens producing method described in claim 20 is a producing method of producing a wafer lens by using the wafer lens molding die described in any one of claims 10 to 17, includes a process of producing multiple sheets of wafer lenses by supplying a hardenable resin material separately between the substrate and each of the lens cavity and the mark cavity; a process of performing positioning by using an alignment mark portion formed by the mark cavity when stacking the multiple sheets of wafer lenses; and a process of joining the stacked wafer lenses.
According to the present invention, the respective optical axes of the lens portions disposed in the stacked wafer lenses can be made coincide with each other at once with sufficient accuracy.
According to the present invention, it becomes possible to provide a wafer lens with sufficient accuracy in which multiple lens portions and alignment mark portions are formed on a substrate, a molding die to mold this wafer lens, and a method of producing a wafer lens.
In
Hereafter, the embodiment of the present invention will be described based on the drawings.
The first master die is used to form a first lens portion and a first alignment mark portion on a first surface of a substrate, and includes a lens master shape portion with a configuration corresponding to the first lens portion and a mark master shape portion with a configuration corresponding to the first alignment mark portion. The second master die is used to form a second lens portion and a second alignment mark portion on a second surface of the substrate, and includes a lens master shape portion with a configuration corresponding to the second lens portion, and a mark master shape portion with a configuration corresponding to the second alignment mark portion.
Here, an example of a lens master shape portion LM is shown in
At Step S101 in
a) shows one example of a lens cavity LC which is formed by being transferred from the lens master shape portion, and each of
a) is a drawing showing a cross sectional surface of one example (corresponding to
In parallel to this, at Step S106 in
Next, description is given to an embodiment to produce a wafer lens by using the first intermediate molding die M1 and the second intermediate molding die M2. Although
Here, a substrate ST made from a parallel plate glass (or resin) is prepared. However, as a previous process, a black resist material is coated on the substrate ST, and exposure via a mask and development are performed for it, whereby multiple apertures may be formed on the first surface S1 and second surface S2 of the substrate ST so as to match with lens portions to be molded. Each aperture exhibits a function of an aperture stop at the time of molding as an imaging lens.
Next, as shown in
On this condition, when light with a prescribed wavelength, such as UV light, is irradiated from the outside, the first resin material PL1 is hardened. Accordingly, with this, on the first surface S1 of the substrate ST, the first lens portions L1 transferred from the lens cavities LC of the first intermediate molding die M1 are formed, and the first alignment mark portions AM1 transferred from the mark cavities MC are formed (Step S105 of
Subsequently, as shown in
Successively, the substrate ST is reversed, and a second resin material PL2 being a light hardenable resin material is dropped in the form of droplets separately on the second surface S2 of the substrate ST (Step S109 in
Here, in the case where the first alignment mark portion AM is shifted from the mark forming section MCc of the mark cavity MC of the second intermediate molding die M2, if molding is performed on this condition, the optical axis of the second lens portion L2 transferred and molded from the lens cavity LC of the second intermediate molding die M2 does not coincide with the optical axis of the first lens portion L1 having been already molded. Then, the second molding die M2 is shifted relatively in the direction orthogonal to the optical axis relative to the substrate ST by a not-shown movable stage. With this, positioning is performed in such a way that the alignment mark AMc of the first alignment mark portion AM1 is made to coincide with the mark forming section MCc of the mark cavity MC of the second intermediate molding die M2. While maintaining this condition, the second intermediate molding die M2 is made to come close to the substrate ST, and as shown in
On such a condition, light with a prescribed wavelength such as UV light is irradiated from the outside, whereby the second resin material PL2 is hardened. With this, the second lens portions L2 are formed on the second surface S2 of the substrate ST (Step S110 in
A diameter φ3 at the highest position (most distant, or furthest separated from the substrate ST) P3 of the lens annular portion Lb is made equal to a diameter φ4 at the highest position P2 of the mark annular portion AMb. Further, a volume at an inside of the lens annular portion Lb in the lens portion L (i.e., when the lens portion L is cut by an imaginary cylindrical surface which is coaxial with an optical axis and passes at the point P3, the volume of the lens portion L which becomes the inside of the imaginary cylindrical surface) is made substantially equal to a volume at an inside of the mark annular portion AMb of the alignment mark portion AM (i.e., when the alignment mark portion AM is cut by an imaginary cylindrical surface which is coaxial with an axis line and passes at the point P4, the volume of the alignment mark portion AM which becomes the inside of the imaginary cylindrical surface). With this, when a resin material is supplied between the substrate ST and each of the molding dies M1 and M2 by the separately-dropping method, it becomes possible to avoid the following problems. When the resin material is supplied too much, a large quantity of the resin material overflows from the mark cavity of the molding die to mold the alignment mark portion AM, and then, the overflowing resin material connects with the neighboring lens portions, which causes cracks at the time of cutting the wafer lens as mentioned later. On the other hand, when the resin material is supplied too small, the alignment mark portion AM cannot be formed with sufficient accuracy.
Furthermore, the configuration of the lens annular portion Lb at an outside from the point P3 is made substantially the same as that of the mark annular portion AMb at an outside from the point P4. This is the same in the alignment mark portion AM shown in each of
c) is a cross-shaped groove formed at the central portion of the flat surface portion AMa, and the alignment mark AMc shown in
Here, the alignment mark portion AM(1) is the same as that shown in
Further, the alignment mark portion AM(2) is the same as that shown in
Furthermore, another wafer lens WL′ is formed through the same process such that a first lens portion L1′ and second lens portion L2′ are formed separately on a substrate ST′. Thereafter, as shown in
Thereafter, an intermediate production body in which the wafer lenses WL and WL′ are jointed to each other is cut out along each of positions indicated with a dotted line shown in
The present invention should not be limited to the embodiment described in the specification, and it is apparent for a person skilled in the art from the embodiment and technical concept described in the specification that the present invention includes the other modification embodiment. The description and the embodiment in the specification are made merely for the purpose of exemplification, and the scope of the present invention is indicated with later-mentioned claims.
For example, stacked layers of a wafer lens are not only two layers, but may be three layers or more. Further, in this embodiment, lenses arranged in the flat surface direction are cut into an individual piece for each lens portion so as to obtain an imaging lens. However, the lenses may be cut for every multiple lenses so as to obtain an imaging lens which includes multiple lenses when being viewed from the optical axis direction. Such an imaging lens can be used as a compound eye lens used for a so-called compound eye type imaging device which obtains an image with higher resolution by synthesizing multiple images obtained at the time that the multiple stacked-lenses arranged in the flat surface direction form the respective images on the respective different positions.
Furthermore, in this embodiment, the intermediate molding die is formed by resin from a machined master die, and a wafer lens is produced by using it. However, a wafer lens may be formed directly from a machined molding die. In this case, although the producing cost increases, it becomes possible to produce a wafer lens with a more exact expected lens configuration. Further, in this case, it is preferable that a concave portion or convex portion adapted to form an alignment mark is processed immediately after processing a mark cavity. Furthermore, in the above embodiment, as a material used for a lens portion, an alignment mark portion, and an intermediate molding die, the light hardenable resin material has been used. However, other energy hardenable resin materials, such as heat hardenable resin materials may be used.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-140887 | Jun 2012 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/066064 | 6/11/2013 | WO | 00 |
