JP2006186295A - Solid-state imaging device and lens and water repellent coating material therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens for solid-state imaging device prevented from coloring, deterioration, deformation in a water existing environment and improved in lens performance, as well as a solid-state imaging device and a water repellent coating material for the device. <P>SOLUTION: The lens for solid-state imaging device is formed on the light receiver of the substrate of the solid-state imaging device having at least the light receiver and a signal transmitter to focus light on the light receiver, is a microlens characterized by having a water repellent layer on the surface. The water repellent coating material for solid-state imaging device contains a water repellent resin and/or a water repellent resin precursor. The solid-state imaging device comprises solid-state imaging device substrate having at least the light receiving part and the signal transmitting part and the microlens placed on the light receiver of the substrate to focus light on it, and has water repellent layer on the surface of the microlens. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lens for a solid-state imaging device, a water repellent coating material for a solid-state imaging device lens, and a solid-state imaging device capable of preventing the degradation of a microlens in a water-existing environment.

  A typical configuration example of a solid-state imaging device will be described with reference to FIG. An image sensor substrate used for a CCD or CMOS is usually formed on the surface of a silicone wafer 1, a signal transfer unit 2 formed on the silicone wafer 1, and the surface of the silicone wafer 1 between the signal transfer units 2. It comprises a light receiving part (photoelectric conversion part) 3 and the like. A lower planarizing film 4 made of a resin is provided on the entire surface of the imaging element substrate. Further, a combination of red, green, and blue (RGB), a combination of cyan, magenta, and yellow (CMY) or a combination corresponding to the spectral characteristics required for each light receiving unit at a position corresponding to the light receiving unit 3 on the lower planarizing film 4 Color filter layers 5 of other colors are formed. An upper planarizing film 6 made of a resin is provided on the entire surface of the color filter layer 5. Further, on the upper planarizing film 6, microlenses 7 for increasing the light collection efficiency of the light receiving unit 3 are selectively arranged at positions corresponding to the color filter layers 5 provided in accordance with the positions of the light receiving unit 3. Is provided. By providing the microlens 7, the amount of light incident on the light receiving unit is increased, and the sensitivity of the solid-state imaging device is improved.

  As a method for forming the microlens 7, the following method is known. (1) A photosensitive resin composition is exposed and developed using a photomask having a predetermined pattern to form a pattern, and the resulting pattern is subjected to a heat treatment (heat flow) to be melted to obtain a photosensitive resin. (2) A lens shape is formed with a photosensitive resin composition on the lens forming material layer in the same manner as in (1), and the lens-shaped photosensitive resin is dried. Etching to transfer the lens shape to the lower layer (lens forming material layer), (3) When pattern exposure is performed on the photosensitive resin composition, the resolving power is adjusted by defocusing, and the lens shape is obtained after development. Method (4) Using a photomask that changes the amount of transmitted light by changing the mask aperture ratio in gradation, the photosensitive resin composition is formed into a lens shape by one exposure and development. How to (gradation exposure method). Of these, the gradation exposure method has attracted attention because it allows precise control of the lens shape.

  Except for the method (2), the microlens 7 is usually formed using a photosensitive resin composition. The photosensitive resin composition contains a transparent resin such as an acrylic resin, a polyimide resin, an epoxy resin, a silicone resin, and the like.

Japanese Patent Laid-Open No. 4-275259

  On the surface of a device such as a solid-state imaging device, foreign matters such as various contaminant species (small pieces, ions, molecules, etc.) generated from the human body, chemicals, device raw materials, etc., and dust in the air adhere to the surface of the device. Since the adhesion of foreign substances can be one of the causes of deteriorating device performance, a process for cleaning the device surface and removing foreign substances is usually provided. There are wet cleaning methods, dry cleaning methods, and other cleaning methods for removing foreign substances adhering to the device surface. Currently, wet cleaning methods using a chemical solution are mainly used. The chemical solution used in the wet cleaning method varies depending on the foreign matter to be removed. When removing a plurality of foreign matters, a plurality of chemical solutions are used. In this case, in order to prevent different chemical solutions from being mixed, a cleaning process using pure water is usually provided after cleaning with each chemical solution.

  However, the microlens provided in the solid-state imaging device often includes a material having a group causing hydrolysis such as an ester group or an amide group from the viewpoint of developability in the lens manufacturing process. In a solid-state imaging device including such a microlens, the lens material may be hydrolyzed in the cleaning process, and the microlens may be colored or deteriorated such as white turbidity or yellowing, or the lens may change in shape due to moisture absorption. In some cases, the surface of the device cannot be carefully cleaned because there is a risk of a change in lens aberration, a focus shift, or the like.

  In addition, devices equipped with solid-state image sensors vary in terms of the period until delivery to the end user after shipment from the manufacturer, and the conditions for storage or use after delivery to the end user. It is required to exhibit desired performance for a desired period under the conditions. Therefore, devices such as solid-state image sensors are shipped from manufacturers, and after undergoing equipment assembly and adjustment processes, a reliability test is performed to confirm that the desired performance and functions are exhibited in a desired period by the end user. Is done.

  In the reliability test, there is one that evaluates the resistance of a device when stored and used in a high temperature and high humidity (for example, 80 ° C., 90% RH) atmosphere. The high temperature and high humidity condition promotes the hydrolysis and moisture absorption due to the ester group and amide group in the microlens as described above. In the conventional solid-state imaging device, the cloudiness of the lens is reduced after the reliability test. Coloring such as yellowing and deformation of the lens were observed.

  Moreover, the microlens containing a polyimide is produced using the fact that a polyimide precursor such as polyamic acid is converted into a polyimide and cured, and heating is required for the conversion from the polyimide precursor to the polyimide. . In general, in order to convert a polyimide precursor to polyimide, it is necessary to heat at a temperature of 200 ° C. or higher, and in order to perform sufficient conversion, heating at about 280 to 300 ° C. is required. It is believed that.

  However, the heating process when forming the microlens of the solid-state imaging device is performed in a state where a coating film made of a lens material is directly formed on the solid-state imaging device substrate provided with a color filter layer, a flattening film or the like. Therefore, when heated to a high temperature such as 280 to 300 ° C., the substrate, the color filter layer, the planarizing film, etc. may be deteriorated.

  Therefore, in order to prevent deterioration of the material below the microlens, in the formation of the microlens in the solid-state imaging device, the heating temperature in the heating process is usually set to about 150 to 250 ° C. in many cases. At such a heating temperature, deterioration of the material below the microlens as described above can be prevented, and curing at a level that maintains the lens shape and lens performance can be obtained. However, since a small amount of unreacted polyimide precursor remains by low-temperature baking, the lens itself is likely to absorb moisture, so that lens deformation and lens turbidity are likely to occur, and the hydrolysis reaction of the lens material is accelerated. Therefore, microlenses containing polyimide or its precursors are colored in a water-existing environment such as a cleaning process or a reliability test, and coloring due to suspension of lens material due to water remaining in the lens through these processes. In addition, the lens transmittance tends to decrease due to the post-process with water remaining in the lens, in particular, coloring due to deterioration under heating conditions. In addition, a change in shape due to moisture absorption of the lens tends to cause a shift in the focal point of the lens, a change in aberration, or the like.

  On the other hand, the formation of microlenses by the gradation exposure method that allows precise control of the lens shape is the heat that forms the lens curved surface by the surface tension when the photosensitive resin pattern is heated and melted by post-baking after development. Unlike the flow method, it is possible to lower the post-bake temperature, and as a method that can reduce the deterioration of the lens material and the damage to the solid-state imaging device substrate and the layers provided on it, it is also attracting attention. Yes. However, post-baking at a low temperature has a problem that the ratio of unreacted polyamic acid remaining in the polyimide resin increases as described above, and the lens is easily deteriorated, colored, and changed in a water-existing environment.

  Conventionally, an additional functional layer is provided on a microlens. For example, Patent Document 1 describes a solid-state imaging device in which an antireflection film made of a predetermined fluorine-containing resin film is formed on a microlens. However, in the solid-state imaging device of Patent Document 1, paying attention to the low refractive index of the fluorine-containing resin, it is only used as an antireflection film, and the deterioration of the lens due to the reaction between the microlens material and water No consideration is given to coloring or shape change.

The present invention has been accomplished in view of the above circumstances, and an object of the present invention is to provide a solid-state imaging element lens in which coloring, deterioration, and shape change in a water-existing environment are prevented and lens performance is improved.
Another object of the present invention is to provide a solid-state image sensor lens coating material used to prevent coloring, deterioration, and shape change of a microlens in a water-existing environment, and a solid-state image sensor including the microlens. To do.

The lens for a solid-state image sensor according to the present invention is a microlens that is formed on the light-receiving unit of a solid-state image sensor substrate on which at least a light-receiving unit and a signal transfer unit are formed, and focuses on the light-receiving unit. A water-repellent layer is provided on the surface.
The lens for a solid-state imaging device of the present invention has water resistance since it has a water-repellent layer on its surface. Therefore, even in the presence of water, a material with insufficient water resistance contained in the microlens reacts with water, typically a hydrolyzable material such as a resin obtained by condensation polymerization by hydrolysis causes hydrolysis. Can be prevented. In addition, it is possible to prevent a shape change due to moisture absorption of the lens. As a result, it is possible to prevent the coloring and deterioration of the microlens, the focus shift of the lens, the change of aberration, and the like caused by the reaction between the material having insufficient water resistance and water.

  In order to further enhance the effect obtained by the water repellent layer, the water repellent layer is preferably provided on the outermost surface of the microlens. When an additional layer other than the water-repellent layer is provided on the microlens surface, the additional layer is provided under the water-repellent layer, thereby imparting water resistance to the lens for the solid-state imaging device including this layer. can do.

An example of a component that imparts water repellency to the water repellent layer is a water repellent resin. As the water repellent resin, an alicyclic resin and / or a silicone resin is preferable. Moreover, a fluorine-containing resin is also preferable as the water-repellent resin.
When the microlens contains a hydrolyzable material, the effect obtained by providing the water repellent layer is increased.
Further, the water repellent layer preferably has a light transmittance of 95% or more at each wavelength in the range of 400 to 750 nm when the film thickness is 50 nm to 500 nm.

The water-repellent coating material for a solid-state imaging element lens of the present invention contains a water-repellent resin and / or a water-repellent resin precursor, and can be used to form the water-repellent layer.
Examples of the water repellent resin include those containing an alicyclic resin and / or a silicone resin. Examples of the water repellent resin precursor include those containing an alicyclic resin precursor and / or a silicone resin precursor.
Further, examples of the water-repellent resin include those containing a fluorine-containing resin, and examples of the water-repellent resin precursor include those containing a fluorine-containing resin precursor.

  Further, when the water repellent coating material for a solid-state imaging element lens is formed into a solidified or cured film having a film thickness of 50 nm to 500 nm, the light transmittance at each wavelength in the range of 400 to 750 nm may be 95% or more. preferable. By forming the water repellent layer with a material capable of forming such a cured film having high light transmittance, a high-performance solid-state imaging element lens can be obtained.

  The solid-state imaging device of the present invention includes at least a solid-state imaging device substrate on which a light-receiving unit and a signal transfer unit are formed, and a microlens that is formed on the light-receiving unit of the solid-state imaging device substrate and focuses on the light-receiving unit. In the solid-state imaging device, a water repellent layer is provided on the surface of the microlens. The solid-state image sensor of the present invention can be suitably used for a solid-state image sensor such as a CCD element or CMOS, or a small solid-state image sensor for a mobile phone.

  The lens for solid-state imaging device of the present invention is provided with a layer having water repellency on the surface of the microlens, so that the microlens material is not easily deteriorated by water or absorbs moisture even in an environment where water exists. In particular, the desired lens shape can be produced by low-temperature baking, so that even a microlens formed by a gradation exposure method, in which a highly hydrolyzable material often remains, sufficiently prevents hydrolysis and moisture absorption. be able to. Therefore, the lens for a solid-state imaging device of the present invention does not cause deterioration or coloring of the microlens due to hydrolysis of the microlens material, shape change due to moisture absorption of the lens, or the like. That is, the lens for a solid-state imaging device of the present invention does not cause deterioration in lens performance due to lens deterioration, coloring, or shape change even in a water-existing environment.

Therefore, the lens for a solid-state imaging device of the present invention and the solid-state imaging device including the lens can sufficiently clean foreign matters such as dust attached to the surface in the manufacturing process with a chemical solution or pure water. By performing such careful cleaning, it is possible to prevent deterioration of the performance of the lens for the solid-state image sensor or the solid-state image sensor due to the adhesion of foreign matter.
In addition, the lens for a solid-state imaging device of the present invention is deteriorated by water in a water-existing environment that may be exposed after shipment from a manufacturer or in one of the reliability test items such as high-temperature and high-humidity storage, particularly water. The lens material does not deteriorate even under conditions that promote disassembly or conditions where the lens absorbs moisture, and the lens shape hardly changes. Can be provided.

The lens for a solid-state image sensor according to the present invention is a microlens that is formed on the light-receiving unit of a solid-state image sensor substrate on which at least a light-receiving unit and a signal transfer unit are formed, and focuses on the light-receiving unit. A water-repellent layer is provided on the surface.
Here, on the microlens surface includes not only the surface of the microlens itself but also the surface of an additional layer provided on the surface of the microlens itself.

  The lens for a solid-state imaging device of the present invention is provided with water resistance by providing a water repellent layer on the surface of the microlens, and the water resistance contained in the microlens is also present in a water-existing environment. Insufficient material does not react with moisture. For this reason, a material with insufficient water resistance reacts with water (typically, hydrolysis of a hydrolyzable material having a hydrolyzable group such as an amide group or an ester group), or a site where water is easily taken up. Microlens coloring (yellowing, cloudiness, etc.), deterioration, lens shape change, etc., which are generated as a result of moisture absorption by a material having, are prevented. That is, it is possible to prevent a decrease in lens performance caused by coloring, deterioration, shape change, and the like of the microlens, and a decrease in light transmittance due to white turbidity of the microlens.

Therefore, the lens for a solid-state imaging device of the present invention can maintain the performance of the lens even after a cleaning step for removing foreign matter adhering to the element surface in the manufacturing process of the solid-state imaging device. That is, it is possible to perform careful cleaning in the presence of water, which has been difficult to perform in the past due to fear of deterioration in lens performance, and further, careful cleaning such as heating in the presence of water. Therefore, it is possible to suppress the performance of the lens for the solid-state image sensor due to the foreign matter adhering to the lens surface, and hence the deterioration of the solid-state image sensor performance due to the foreign matter attached to the surface of the solid-state image sensor.
In addition, the lens for a solid-state imaging device of the present invention may be colored or deteriorated as described above even in a water-existing environment that may be exposed after shipment from a manufacturer or in a high-temperature and high-humidity condition in a reliability test. Since deformation of the shape is prevented, a highly reliable solid-state imaging device can be provided.

In the lens for a solid-state imaging device of the present invention, the water repellent layer provided on the surface of the microlens is provided on the outermost surface when an additional layer other than the water repellent layer is provided on the microlens surface. It is preferable. By providing the water repellent layer on the outermost surface, it will have water resistance including the additional layer provided on the surface of the microlens, and with the microlens itself, additional layers may be colored, deteriorated, changed in shape, etc. Can be prevented.
If the additional layer provided on the surface of the microlens has water resistance or needs to be provided on the upper layer side of the water repellent layer, the water repellent layer is not necessarily solid-state imaging. It does not have to be provided on the outermost surface of the element lens.

  The water repellent layer has higher water repellency than the material forming the microlens and can repel moisture. When an additional layer is provided between the microlens and the water repellent layer, it is preferable that the layer has a higher water repellency than the material forming the additional layer and the material forming the microlens.

As a measure of the water repellency of the material forming the water repellent layer, the contact angle with water (water contact angle) is preferably 30 to 120 ° larger than that of the material forming the microlens. In order to form a water repellent layer having sufficient water repellency, the water contact angle of the material forming the water repellent layer is preferably 75 ° or more, particularly 80 ° or more, and more preferably 100 ° or more. Is preferred.
The water contact angle was determined by dropping 10 μl of pure water onto a smooth surface formed using a material for forming the water repellent layer, microlens, and additional layer, and measuring the value after 10 seconds using a contact angle meter ( It was measured using Kyowa Interface Science Co., Ltd. CA-Z type). As a measurement method using a contact angle meter, a droplet method (1 / 2θ method) was used.

  Here, the droplet method will be described with reference to FIG. The angle between the horizontal line at the solid-liquid interface and the tangent line at the droplet edge is θA (contact angle), and the angle between the horizontal line at the solid-liquid interface and the line connecting the droplet apex and the droplet edge is θB (measurement angle). Assuming that the droplet shape is a part of a circle, the relationship 2θB = θA is established. Using this relationship, the contact angle θA is obtained from the measured θB, the apex height h, and the water droplet radius r.

The component (water repellent material) for imparting water repellency to the water repellent layer is not particularly limited as long as it can impart water repellency as described above to the water repellent layer. The water contact angle of the water repellent material is preferably 75 ° or more, particularly 80 ° or more, and more preferably 100 ° or more. Specific water-repellent materials include water-repellent resins such as alicyclic resins, silicone resins and fluorine-containing resins, acrylic resin compositions containing water-repellent particles such as silica fine particles and fluorine-containing fine particles, and water-repellent materials. A vapor-deposited film such as a metal, metal oxide or metal nitride.
Among these, alicyclic resins, silicone resins and fluorine-containing resins are preferable from the viewpoints of transparency, heat resistance and production cost, and alicyclic resins are particularly preferable from the viewpoint of low hygroscopicity.

  The alicyclic resin in the present invention is not particularly limited as long as it contains an alicyclic structure in the main chain and / or side chain and has water repellency, but from the viewpoint of mechanical strength, heat resistance, and transparency, Those containing an alicyclic structure in the main chain are preferred. In particular, those having a structure in which the alicyclic structure is linearly linked in the main chain are preferred. At this time, an acyclic hydrocarbon group having about 1 to 4 carbon atoms (which may have a branched structure) may be interposed between the alicyclic structures constituting the main chain. The side chain which has an alicyclic structure may couple | bond with the alicyclic structure which comprises. When the hydrocarbon group interposed between the alicyclic structures constituting the main chain is an acyclic hydrocarbon group having 5 or more carbon atoms, the acyclic hydrocarbon group is easily oxidatively decomposed by heat, and the alicyclic resin There is a risk that the heat resistance of the will be reduced.

  The alicyclic structure may be composed only of a saturated bond or may contain an unsaturated bond. From the viewpoint of heat resistance and light resistance, a structure composed only of a saturated bond is preferable. Specific examples of the alicyclic structure include a cycloalkane structure and a cycloalkene structure, and the cycloalkane structure is preferable from the viewpoint described above. The number of carbon atoms constituting the ring of the smallest unit of the alicyclic structure is not particularly limited, but 3 to 20, preferably 4 to 15, particularly preferably 4 to 4 in consideration of heat resistance and light resistance. Nine.

  However, like polycyclohexyl acrylate, an alicyclic resin having an alicyclic structure in the side chain and having the alicyclic structure portion connected to the main chain by a hydrolyzable bond is repellent by hydrolysis. It is not suitable because it tends to cause a decrease in water and color and may deteriorate the performance of the water repellent layer.

The alicyclic structure contained in the alicyclic resin may be one type or two or more types, and can be appropriately combined as necessary.
The alicyclic resin may contain a repeating unit other than the repeating unit having an alicyclic structure, but from the viewpoint of transparency, water repellency, etc., the repeating unit having an alicyclic structure is 20 to 100 mol%. In particular, those containing 40 to 100 mol% are preferable. In addition, from the viewpoint of low hygroscopicity, the repeating unit other than the alicyclic structure contained in the alicyclic resin is preferably a hydrocarbon group having no polarity.

Specific examples of the alicyclic resin include a monocyclic olefin polymer, a polycyclic olefin polymer, a monocyclic olefin polymer having an unsaturated bond, and an unsaturated bond. Examples thereof include polycyclic cyclic olefin polymers and hydrogenated products thereof. Among these, from the viewpoint of heat resistance and mechanical strength, polycyclic olefin polymers, polycyclic olefin polymers having an unsaturated bond, and hydrogenated products thereof are preferable. For example, adamantane ring, norbornane ring, tricyclo [5.2.1.0 ^{2, 6]} decane ring, tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] 2~4 ring of the cyclic olefin polymer such as dodecane ring.

Specific examples of the alicyclic structure include, for example, a cycloalkane ring having about 3 to 20 carbon atoms such as a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cyclohexene ring, a cyclooctane ring, a cyclodecane ring, and a cyclododecane ring. Or cycloalkene ring, monocyclic alicyclic ring such as lactone ring; perhydroindene ring, decalin ring, perhydrofluorene ring, perhydroanthracene ring, perhydrophenanthrene ring, perhydroacenaphthene ring, perhydrophenalene ring, norbornane ring, norbornene ring, pinane ring, a bornane ring, Isoboruniran ring, adamantane ring, tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodecane ring, lactone ring, bicyclo [2.2.1] heptane ring, bicyclo [3.3 .0] Octane ring, tricyclo [5.2.1.0 ^2,6 ] decane ring, pentacyclo [6.5.1.1 ^3,6 .0 ^2,7 .0 ^9,13] pentadecane ring, pentacyclo [7.4.0.1 ^2,5 .1 ^9,12 .0 ^8,13] pentadecane ring, tricyclo [4.4.0.1 ^{2, 5]} undecane ring, pentacyclo [8.4. 0.1 ^2,5 .1 ^9,12 .0 ^8,13] hexadecane ring, heptacyclo ^{[8.7.0.1 3,6 .1 10,17 .1 12,15 .0} 2,7 .0 11,16] eicosane ring, heptacyclo ^{[8.8.0.1 4,7 .1 11,18 .1 13,16 .0} 3,8 .0 12,17] heneicosan polycyclic alicyclic having or not having an unsaturated bond in the ring or the like the recited, in particular, bicyclo [2.2.1] heptane ring, bicyclo [3.3.0] octane ring, tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodecane ring, tricyclo [5.2.1.0 ^{2, 6]} decane A ring or the like is preferable.

As the alicyclic resin, a cycloolefin polymer having a main chain in which these alicyclic structures are linearly connected is preferable. In this cycloolefin polymer, an acyclic hydrocarbon group having about 1 to 4 carbon atoms having a methylene chain or a branched structure may be interposed between the alicyclic structures constituting the main chain, and also constitutes the main chain. A side chain having an alicyclic structure may be bonded to the alicyclic structure.
Since such an alicyclic resin consisting only of hydrocarbon groups does not have a polar group, it has low hygroscopicity. Therefore, a water-repellent layer formed using an alicyclic resin having no polar group is less likely to be deformed due to moisture absorption, and is less likely to change its shape due to changes in the humidity of the surrounding environment or contact with water. In addition, lens shape change, lens deterioration, coloring, and the like due to the water absorbed by the water repellent layer reaching the lens are unlikely to occur. Therefore, when a water-repellent layer is formed using an alicyclic resin that does not have a polar group, there are problems such as changes in the humidity of the surrounding environment, lens aberration changes due to contact with water, defocus, and light transmission degradation. Can be further prevented.

On the other hand, even if the molecule as a whole has water repellency, when water is dripped onto a material that has polar groups and has hygroscopicity locally, most of the water is repelled by water repellency. However, a very small part of the moisture may be absorbed by the polar group. In addition, such a material may absorb water vapor in the atmosphere from polar groups. In other words, even if the molecule as a whole has water repellency, a water-repellent layer is formed of a material having a polar group and hygroscopicity even locally, the water changes due to humidity changes in the surrounding environment and contact with water. May be absorbed and the shape of the water-repellent layer may change.
Furthermore, some materials are difficult to return to the shape before moisture absorption after drying. In addition, when the water absorbed from the polar group reaches the lens positioned below the water-repellent layer, the shape of the lens changes or deteriorates.

  Accordingly, it is preferable that the hygroscopicity is as small as possible. However, silicone resins and fluorine-containing resins, which will be described later, have high water repellency, but since many of them have polar groups, they are not completely hygroscopic. If the content of polar groups is reduced to reduce hygroscopicity, silicone-based resins and fluorine-containing resins not only have water repellency due to the presence of siloxane skeletons and fluorine atoms, but oil repellency becomes too strong, resulting in water-repellent coating materials. There is a problem that the applicability of the coating deteriorates. Silicone resins and fluorine-containing resins are usually used together with additives such as surfactants to improve coatability, but these additives reduce the water-repellent performance of the water-repellent layer. Or increase hygroscopicity. Therefore, when a silicone resin or a fluorine-containing resin is used as the water-repellent resin, it is difficult to obtain a water-repellent layer having a moisture absorption lower than that of the alicyclic resin while maintaining the applicability of the water-repellent coating material.

On the other hand, the alicyclic resin is excellent in applicability of the water-repellent coating material and has an appropriate repellent property, even if it does not have a polar group or does not use an additive such as a surfactant. A water-repellent layer having aqueous properties and low hygroscopicity can be obtained.
The alicyclic resin is preferably composed of only a hydrocarbon group from the viewpoint of the hygroscopicity of the water repellent layer and preferably has no polar group. However, in order to improve the applicability of the water repellent coating material, A repeating unit in which a polar group or a group having a polar group is bonded to an alicyclic structure constituting a chain may be included (a polar group or a group having a polar group does not constitute a main chain skeleton). In this case, a repeating unit in which a polar group or a group having a polar group is bonded to the alicyclic structure constituting the main chain so as to balance the hygroscopicity of the water repellent layer and the applicability of the water repellent coating material, The ratio with respect to all repeating units constituting the main chain is preferably about 1 to 40 mol%, and particularly preferably 1 to 20 mol%. Here, examples of the polar group include a carboxyl group, an ester group, an amino group, an amide group, a silanol group, a glycidyl ether group, an ether group, and a hydroxyl group.

  Further, when an alicyclic resin is used as a water-repellent resin, a water-repellent coating material having good coating properties can be obtained without using an additive such as a surfactant such as a silicone resin or a fluorine-containing resin. In many cases, an additive may be used to further improve the coating property. However, from the viewpoint of the hygroscopicity and water repellency of the lens, the surfactant is preferably suppressed to 0.01 to 5% by weight, particularly about 0.01 to 1% by weight, based on the solid content of the water-repellent coating material. In the case of a silicone-based resin or a fluorine-containing resin, which will be described later, in order to obtain a sufficient effect of improving the coatability by a surfactant, it must be added in a larger amount than the above range, and an alicyclic resin is used. It is difficult to reduce hygroscopicity compared to the case.

  The molecular weight of the alicyclic resin contained in the water-repellent layer in the present invention may be appropriately selected, but the weight average molecular weight is preferably in the range of 500 to 100,000, and in the range of 2,000 to 50,000. More preferably. When the weight average molecular weight is in the range of 500 to 100,000, a resin excellent in water repellency, mechanical strength, heat resistance and spin coating suitability can be obtained.

  Silicone resins have the advantage of being able to relieve film stress because of their high elastic modulus. The silicone resin in the present invention is not particularly limited as long as it contains a siloxane unit (repeating unit having a siloxane structure) in the main chain and / or side chain and has water repellency, but can reduce water repellency and film stress. From the viewpoint of low elasticity and coating suitability, those containing a siloxane unit in the main chain are preferred.

One type or two or more types of siloxane units may be contained in the silicone-based resin, and they can be combined as appropriate.
The silicone resin may contain a repeating unit other than the siloxane unit. However, from the viewpoint of water repellency, low elasticity capable of reducing film stress, and coating suitability, the siloxane unit is contained in an amount of 20 to 100 mol%, particularly 40. Those containing ˜100 mol% are preferred.

  Examples of the siloxane compound constituting the silicone-based resin include an organosilicon compound represented by the following general formula (1) and / or a hydrolyzate thereof.

(Where R1 is an organic group having 1 to 10 carbon atoms, R2 is a hydrocarbon group or halogenated hydrocarbon group having 1 to 6 carbon atoms, X is a hydrolyzable group, and a and b are 0 or 1) X may be different or the same, and R1 and R2 may be the same.

  Specific examples include tetraalkoxysilanes such as methyl silicate, ethyl silicate, n-propyl silicate, i-propyl silicate, n-butyl silicate, sec-butyl silicate, and t-butyl silicate, and hydrolysis thereof. object;

  Methyltrimethoxysilane, methyltriethoxysilane, methyltrimethoxyethoxysilane, methyltriacetoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane , Vinyltriacetoxysilane, vinyltrimethoxyethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriacetoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropyltriethoxysilane, γ-chloropropyltriacetoxysilane , Γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-merca Topropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, β-cyanoethyltriethoxysilane, methyltriphenoxysilane, chloromethyltrimethoxysilane, chloro Methyltriethoxysilane, glycidoxymethyltrimethoxysilane, glycidoxymethyltriethoxysilane, α-glycidoxyethyltrimethoxysilane, α-glycidoxyethyltriethoxysilane, β-glycidoxyethyltrimethoxysilane , Β-glycidoxyethyltriethoxysilane, α-glycidoxypropyltrimethoxysilane, α-glycidoxypropyltriethoxysilane, β-glycidoxypropyltrimethoxysilane, β-glycidoxypropyltriethoxy Sisilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltripropoxysilane, γ-glycidoxypropyltributoxysilane, γ-glycidoxypropyltrimethoxy Ethoxysilane, γ-glycidoxypropyltriphenoxysilane, α-glycidoxybutyltrimethoxysilane, α-glycidoxybutyltriethoxysilane, β-glycidoxybutyltrimethoxysilane, β-glycidoxybutyltri Ethoxysilane, γ-glycidoxybutyltrimethoxysilane, γ-glycidoxybutyltriethoxysilane, δ-glycidoxybutyltrimethoxysilane, δ-glycidoxybutyltriethoxysilane, (3,4-epoxycyclohexyl) ) Methyltrimethoxy Lan, (3,4-epoxycyclohexyl) methyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, β- (3, 4-epoxycyclohexyl) ethyltripropoxysilane, β- (3,4-epoxycyclohexyl) ethyltributoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxyethoxysilane, γ- (3,4-epoxycyclohexyl) ) Propyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriphenoxysilane, γ- (3,4-epoxycyclohexyl) propyltrimethoxysilane, γ- (3,4-epoxycyclohexyl) propyltriethoxysilane , Δ- (3,4 Epoxycyclohexyl) butyl trimethoxy silane, .delta. (3,4-epoxycyclohexyl) trialkoxysilane such as butyl triethoxysilane, triacyloxy silane or tri phenoxy silanes or their hydrolysates;

  Dimethyldimethoxysilane, phenylmethyldimethoxysilane, dimethyldiethoxysilane, phenylmethyldiethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropylmethyldiethoxysilane, dimethyldiacetoxysilane, γ-methacryloxypropylmethyldimethoxysilane , Γ-methacryloxypropylmethyldiethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyldiethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, methylvinyldimethoxysilane, Methylvinyldiethoxysilane, glycidoxymethylmethyldimethoxysilane, glycidoxymethylmethyldiethoxysilane, α-glycidoxyethyl Methyldimethoxysilane, α-glycidoxyethylmethyldiethoxysilane, β-glycidoxyethylmethyldimethoxysilane, β-glycidoxyethylmethyldiethoxysilane, α-glycidoxypropylmethyldimethoxysilane, α-glycid Xylpropylmethyldiethoxysilane, β-glycidoxypropylmethyldimethoxysilane, β-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ -Glycidoxypropylmethyldipropoxysilane, γ-glycidoxypropylmethyldibutoxyethoxysilane, γ-glycidoxypropylmethyldimethoxyethoxysilane, γ-glycidoxypropylmethyldiphenoxysilane, γ-glycid Cypropylmethyldiacetoxysilane, γ-glycidoxypropylethyldimethoxysilane, γ-glycidoxypropylethyldiethoxysilane, γ-glycidoxypropylvinyldimethoxysilane, γ-glycidoxypropylvinyldiethoxysilane, γ -Dialkoxysilanes such as glycidoxypropylphenyldimethoxysilane, γ-glycidoxypropylphenyldiethoxysilane, diphenoxysilane, diacyloxysilanes or hydrolysates thereof, but are not limited thereto, and Other silane coupling agents that are used can be used.

  The molecular weight of the silicone resin contained in the water-repellent layer of the present invention may be appropriately selected, but the weight average molecular weight is preferably in the range of 500 to 100,000, particularly in the range of 1,000 to 70,000. More preferably. When the weight average molecular weight is in the range of 500 to 100,000, a resin excellent in water repellency, mechanical strength, heat resistance and spin coating suitability can be obtained.

The fluorine-containing resin in the present invention is not particularly limited as long as it contains fluorine bonded directly to the main chain and / or bonded to the side chain and has water repellency, but from the viewpoint of water repellency and heat resistance, an aromatic ring In particular, those containing a fluorine-substituted aromatic ring are preferred.
The structure of the main chain skeleton of the fluororesin is not particularly limited, and may be aliphatic, aromatic, or a structure containing both of them. The aliphatic system may be linear, have a branched structure, or have an alicyclic structure, and may contain a hetero atom. The aromatic system may contain a hetero atom, or may contain a structure in which an alicyclic structure is condensed with an aromatic ring.

The repeating unit containing fluorine constituting the fluorine-containing resin may be one type or two or more types, and can be appropriately combined as necessary.
Further, the fluororesin may contain a repeating unit other than the repeating unit containing fluorine, but from the viewpoint of water repellency and heat resistance, the repeating unit containing fluorine is 30 to 100 mol%, particularly 50 to 100 mol. % Is preferable.

  Specific fluorine-containing resins include those obtained by polymerization of fluorine-containing reactive monomers or copolymerization with other reactive monomers. The monomer species and combinations thereof are fluorine-containing reactions. It is not particularly limited as long as it can be polymerized with the reactive monomers or can be copolymerized with other reactive monomers.

Examples of the fluorine-containing reactive monomer include perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether), perfluoro (propyl vinyl ether), perfluoro (butyl vinyl ether), perfluoro (isobutyl vinyl ether), perfluoro ( Perfluoro (alkyl vinyl ether) or perfluoro (alkoxyalkyl vinyl ether) such as propoxypropyl vinyl ether; general formula CH ₂ ═CH—O—Rf (wherein Rf represents an alkyl group or alkoxyalkyl group containing a fluorine atom) ) (Fluoroalkyl) vinyl ethers or (fluoroalkoxyalkyl) vinyl ethers; vinylidene fluoride, chlorotrifluoroethylene, 3,3,3-trifluoropropylene, Fluoroolefins such as trifluoroethylene; 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3,3-pentafluoropropyl (meth) acrylate, 2- (perfluorobutyl) ethyl ( Fluorine-containing (meth) acryl such as (meth) acrylate, 2- (perfluorohexyl) ethyl (meth) acrylate, 2- (perfluorooctyl) ethyl (meth) acrylate, 2- (perfluorodecyl) ethyl (meth) acrylate Examples include, but are not limited to, acid esters.

  Examples of other reactive monomers copolymerized with the fluorine-containing reactive monomer include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, n Alkyl vinyl ethers or cycloalkyl vinyl ethers such as pentyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, n-dodecyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexyl vinyl ether; vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate , Vinyl carboxylates such as vinyl caproate, vinyl versatate, vinyl stearate; ethylene, propylene, Α-olefins such as sobutene; methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) And (meth) acrylic acid esters such as acrylate and 2- (n-propoxy) ethyl (meth) acrylate.

  The molecular weight of the fluorine-containing resin used in the present invention may be appropriately selected, but is preferably in the range of 1,000 to 50,000, and in the range of 1,000 to 20,000 in terms of weight average molecular weight. It is more preferable. When the weight average molecular weight is in the range of 1,000 to 50,000, a resin excellent in water repellency, mechanical strength, heat resistance, and spin coating suitability can be obtained.

The refractive index of the water repellent layer and the water repellent coating material used for forming the solidified or hardened material is preferably smaller than that of the microlens material. This is because an antireflection effect can be obtained by making the refractive index of the water repellent layer smaller than that of the microlens. By preventing reflection of incident light on the surface of the microlens, it is possible to improve the light collection efficiency of the microlens and to suppress the generation of noise. Specifically, the refractive index of the water repellent layer is preferably about 0.05 to 0.60, particularly about 0.15 to 0.60 smaller than the microlens material. More specifically, when the average refractive index of the microlens material in light having a wavelength of 400 to 750 nm is in the range of 1.50 to 1.90, the water repellent layer (that is, the water repellent layer is formed). The water-repellent coating material used for the purpose is a solid or cured material) having an average refractive index with respect to light having a wavelength of 400 to 750 nm within a range smaller than the refractive index of the microlens material. It is preferable to be within the range of 1.20 to 1.50.
Further, it is preferable that the value of R in the following reflectance formula (1) is as close to 0 as possible.

  Here, when the average refractive index in the light having a wavelength of 400 to 750 nm is in the range of 1.20 to 1.50, the refractive index in all the light having the wavelength in the above range is 1.20 to 1.50. It is a value obtained by dividing the sum of the measured values of the refractive index for each light having a wavelength in the above range by the number of measurement points.

Of the resins exemplified above as the water repellent material, the fluororesin is preferable from the viewpoint of antireflection because a resin having a particularly low refractive index can be selected.
In general, the fluorine-containing resin often has a refractive index lower than that of the lens material, and most of them have an average refractive index in the range of 1.50 or less in light having a wavelength of 400 to 750 nm. Almost all the fluororesins have an average refractive index in the above range. From the viewpoint of low refractive index, those containing 0.1 to 40% by weight of fluorine in the molecule are preferred, and those containing 5 to 40% by weight are particularly preferred.

An alicyclic resin and a silicone-based resin suitable for forming a water-repellent layer having an antireflection effect may be appropriately selected according to the refractive index of the lens material. For example, as the alicyclic resin, the refractive index decreases as the ratio of the alicyclic structure constituting the main skeleton, particularly the polycyclic alicyclic structure increases, and as the ratio of the aromatic ring constituting the main skeleton decreases. Therefore, it is particularly preferable that the main skeleton is composed of only a polycyclic alicyclic structure. Moreover, as a silicone type resin, what contains a fluorine atom is preferable, For example, what substituted a part of hydrogen atom in resin with a silicone main frame | skeleton by fluorine etc. is mentioned.
Since the alicyclic resin and the silicone-based resin are less expensive materials than the fluorine-containing resin, there is an advantage that the cost of the lens for the solid-state imaging element can be reduced. Moreover, as will be described later, the alicyclic resin and the silicone-based resin have an advantage that they are excellent in coatability and can easily form a water repellent layer having a desired film thickness.

The water repellent layer may contain only one type of water repellent material, or may contain two or more types of water repellent material. Or, the repeating unit of each water-repellent resin such as silicone resin, alicyclic resin, and fluorine-containing resin is copolymerized or substituted, such as those in which some hydrogen atoms in a resin having a silicone main skeleton are fluorine-substituted. A resin coexisting in one molecule may be used. The water repellent material is usually contained in the water repellent layer at about 30 to 95% by weight, preferably 50 to 95% by weight, particularly preferably 60 to 95% by weight. When the content of the water repellent material in the water repellent layer is less than 30% by weight, sufficient water repellency may not be obtained. On the other hand, when the content of the water repellent material in the water repellent layer exceeds 95% by weight, it may be repelled to the lower layer when the water repellent coating material is applied, and it is difficult to apply uniformly. The adhesion between the lower layer and the water repellent layer may be poor.
In the water-repellent layer, components other than the water-repellent material described above can be blended as necessary. Examples of other components include, but are not limited to, resins other than those described above, silane coupling agents, surfactants, antioxidants, adhesion promoters, and other additives.

The water-repellent layer can be formed of a water-repellent coating material containing the above-described water-repellent resin and / or a precursor of these water-repellent resins and, if necessary, other components. Here, the water-repellent resin precursor is a component that becomes a water-repellent resin by reacting in the solidification and / or curing step when forming the water-repellent layer.
For example, the alicyclic resin precursor is not particularly limited as long as it becomes an alicyclic resin as described above after the solidification and / or curing step, for example, a reactive group such as a glycidyl group or an oxetanyl group. And alicyclic monomers and oligomers having In order to make such an alicyclic resin precursor an alicyclic resin, in the curing step, it is usually heated to 100 ° C. to 250 ° C. and / or with a wavelength in the visible and invisible regions as necessary. Irradiate light such as ultraviolet rays, electromagnetic waves and radiation.

  The silicone resin precursor is not particularly limited as long as it becomes a silicone resin as described above after the solidification and / or curing step. For example, the above-described organosilicon compound and / or a hydrolyzate thereof are used. Is mentioned. In order to make such a silicone-based resin precursor into a silicone-based resin, in the curing step, it is usually heated to 25 ° C. (room temperature) to 230 ° C., and in some cases 100 to 230 ° C., and / or as necessary. And irradiating light such as ultraviolet rays, electromagnetic waves and radiation having wavelengths in the visible and invisible regions.

As a method for forming a water-repellent layer made of a silicone-based resin, for example, a method using a sol-gel method can be given as a general method. When the sol-gel method is used, the organic silicon compound contained in the water-repellent coating material is hydrolyzed into a condensate, so that the water-repellent coating material usually contains a buffer solution or acid-derived water. Such water is preferably contained in an amount such that the lens does not absorb moisture or deteriorate, specifically 0.1 to 10% by weight in the water-repellent coating material. However, since the water-repellent coating material containing a silicone resin is heated at a temperature of 100 ° C. to 230 ° C. exceeding the boiling point of water immediately after application as described above, the water content is not greatly affected. In the case of using a silane coupling agent, it is preferable to proceed the reaction under temperature and humidity conditions at a level where the lens does not absorb moisture. In particular, those that proceed and cure at room temperature (about 25 ° C.) are more preferred.
In the case of a material in which a fluorine-containing group is introduced into the main skeleton made of a silicone precursor, the method for curing the water-repellent layer made of the above-described silicone resin is applied.

  The fluorine-containing resin precursor is not particularly limited as long as it becomes a fluorine-containing resin as described above after the solidification and / or curing step, and examples thereof include the fluorine-containing reactive monomer described above. . In order to make such a fluorine-containing resin precursor into a fluorine-containing resin, in the curing step, it is usually heated to 100 ° C. to 250 ° C. and / or ultraviolet rays having a wavelength in the visible and invisible regions as necessary, Irradiate light such as electromagnetic waves and radiation.

The water-repellent coating material is used for curing a radically polymerizable monomer or a cationically polymerizable monomer, which is a precursor of an additional resin other than the water-repellent resin, and a resin composed of the water-repellent resin or the water-repellent resin precursor. Polymerization of the radically polymerizable monomer or cationically polymerizable monomer, or the radically polymerizable monomer or cationically polymerizable monomer that becomes a precursor of an additional resin other than the water-repellent resin, or the above-described water-repellent resin precursor is started. May contain components such as a radical polymerization initiator or a cationic polymerization initiator. For example, heat / photocuring can be performed at a lower temperature by adding a cationic polymerization initiator that generates an acid by light or heat. Further, by adding a compound having a reactive double bond and a photo radical polymerization initiator, a water repellent resin can be obtained by irradiation with UV light.
From the viewpoint of adhesion and adhesion of the water-repellent layer to the lower layer such as a lens and other additional layers, a water-repellent coating material containing a water-repellent resin precursor, a radical polymerizable monomer, a cationic polymerizable monomer, etc. It is preferable to form a water repellent layer by curing.

The water-repellent coating material is prepared by dissolving or dispersing in a solvent such that the solid content concentration of the components as described above is 0.5 to 30% by weight and removing insolubles by filtration.
When a fluorine-containing resin is used as the water-repellent material, it is preferable to prepare the water-repellent coating material so that the solid concentration of the fluorine-containing resin is about 0.5 to 15% by weight from the viewpoint of coatability.

On the other hand, when a silicone resin and / or alicyclic resin is used as the water repellent material, the silicone resin solid content concentration or the alicyclic resin solid content concentration is about 0.5 to 30% by weight, It is preferable to prepare a water repellent coating material. Since the alicyclic resin and the silicone-based resin have low viscosity and excellent coating properties, the amount of the solvent in the water-repellent coating material may not be increased. A high solid content means that there is no significant difference in film thickness and shape between the coating film immediately after application of the water repellent coating material and the cured film (water repellent layer), and the desired film thickness and shape. There is an advantage that it is easy to form a water-repellent layer having water. In addition, the temperature and time for curing the coating film can be made mild.
The solvent is not particularly limited as long as it satisfies the solubility of each component and the coating property of the water-repellent coating material, and a commonly used solvent can be used.

  Specific examples of the solvent include alcohol solvents such as methyl alcohol, ethyl alcohol, N-propyl alcohol and i-propyl alcohol; cellosolv solvents such as methoxy alcohol and ethoxy alcohol; carbitols such as methoxyethoxyethanol and ethoxyethoxyethanol. Solvents; Ester solvents such as ethyl acetate, butyl acetate, methyl methoxypropionate, ethyl methoxypropionate, ethyl ethoxypropionate, ethyl lactate, propylene glycol monomethyl ether acetate; ketone solvents such as acetone, methyl isobutyl ketone, cyclohexanone Methoxyethyl acetate, methoxypropyl acetate, methoxybutyl acetate, ethoxyethyl acetate, ethyl cellosolve acetate, etc. Cellosolve acetate solvents; carbitol acetate solvents such as methoxyethoxyethyl acetate and ethoxyethoxyethyl acetate; ether solvents such as diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and tetrahydrofuran; N, N-dimethylformamide, N, N- Aprotic amide solvents such as dimethylacetamide and N-methylpyrrolidone; lactone solvents such as γ-butyrolactone; unsaturated hydrocarbon solvents such as benzene, toluene, xylene and naphthalene; N-heptane, N-hexane, N- Organic solvents such as saturated hydrocarbon solvents such as octane.

Among these solvents, esters such as ethyl acetate, ethyl lactate, ethyl methoxypropionate, ethyl ethoxypropionate, propylene glycol monomethyl ether acetate and γ-butyllactone, lactone solvents and ether solvents are preferably used.
Further, when the water-repellent coating material for forming the water-repellent layer containing the silicone resin is a sol-gel reaction liquid, alcohol such as ethanol or a buffer solution is used.

  The water-repellent layer may be provided on the surface of the microlens itself, or when an additional layer is provided on the surface of the microlens itself. Examples of the additional layer provided on the surface of the microlens include an antireflection film, an infrared cut filter, and an ultraviolet cut filter. When the water repellent layer has an antireflection effect, the antireflection film may not be provided.

The method for forming the water repellent layer on the surface of the microlens is not particularly limited, and a general method can be used as long as the water repellent layer having a desired film thickness can be formed. For example, a method of applying a water-repellent coating material on a microlens or a layer formed on the microlens, drying and solidifying, and curing as necessary.
The application method of the water repellent coating material is not particularly limited, and may be appropriately selected from application methods such as spin coating, slit & spin coating, spray coating, cap coating, and die coating. The drying and curing conditions of the applied water repellent coating material may be set as appropriate. Moreover, a water repellent layer can also be formed on the microlens surface by a vapor deposition method.

The film thickness of the water repellent layer may be appropriately determined within a range having sufficient water repellency, but may be determined in consideration of the optical characteristics of the obtained microlens, the performance of a solid-state imaging device provided with the microlens, and the like. preferable. For example, in the microlens provided in the solid-state imaging device, the height of the convex portion at the highest position is usually about 0.3 to 2 μm. The film thickness of the water-repellent layer provided on the surface of the microlens having such a height is usually preferably nano-order, that is, about 1 to 999 nm, and particularly preferably about 50 to 500 nm. .
When further providing an antireflection effect to the water repellent layer, the film thickness of the water repellent layer may be determined in consideration of the refractive index of the microlens material, the refractive index of the water repellent layer material, the wavelength of incident light, etc. preferable. In particular, the film thickness of the water repellent layer is preferably approximately λ / (4 × n ₁ ) with respect to the wavelength λ of incident light. Here, n ₁ is the average refractive index of the water-repellent layer, similarly to n ₁ in the reflectance formula (1).

  Further, when the film thickness of the water repellent layer is in the range of 50 to 500 nm, the transmittance of the water repellent layer for light at each wavelength in the range of 400 to 750 nm is preferably 90% or more, particularly 95% or more. Preferably there is. That is, when the water repellent coating material for forming the water repellent layer is a solidified or cured film having a film thickness of 50 to 500 nm, the light transmittance at each wavelength in the range of 400 to 750 nm is 90% or more, particularly 95%. The above is preferable.

The present invention is a solid-state imaging that does not react with water or absorb moisture in the presence of water even if it is a microlens formed of a material with insufficient water resistance, and therefore does not cause deterioration, coloring, or moisture absorption shape change. An element lens is provided. Therefore, as a material for the microlens, a material having insufficient water resistance, typically a material having hydrolyzability, can be suitably used. The material having hydrolyzability has a hydrolyzable group, and examples thereof include a resin obtained by condensation polymerization by hydrolysis. Usually, the alkali-soluble resin contained in the material forming the microlens is often a group having hydrolyzability, and the group exhibiting alkali-solubility corresponds to a resin having hydrolyzability.
The alkali-soluble resin is not particularly limited, and examples thereof include those having a hydrolyzable group such as an ester group, an amide group, an imide group, a urea group, and a urethane group, or uncured hydrolysates thereof.

Specifically, those having a hydrolyzable group as described above and having an imide skeleton and / or a siloxane skeleton, polyacrylic acid, polymethacrylic acid, acrylic acid copolymer, methacrylic acid copolymer, etc. Examples thereof include acrylic resins and resins containing phenolic hydroxyl groups.
Among them, as described above, a microlens made of a polyimide resin formed from a polyimide precursor having an amide group such as polyamic acid cannot be sufficiently cured by high-temperature heating from the viewpoint of preventing deterioration of adjacent members. For this reason, usually, unreacted polyamic acid is often contained, and coloring due to hydrolysis tends to occur. In addition, if there are amino groups, carboxylic acid groups and unreacted amic acids generated as hydrolysates, they are present as salts, so the lens is likely to absorb moisture, causing phase separation from other polymer parts, and easily causing white turbidity. . In addition, the shape is likely to change due to moisture absorption of the lens. Therefore, the effect of the present invention is particularly great in a lens for a solid-state imaging device including a microlens made of such a polyimide resin.

In the present invention, the microlens may be formed of a material other than a material having insufficient water resistance, such as a hydrolyzable resin as described above.
In addition, according to the present invention, it is possible to form a microlens using a material that has been difficult to put into practical use because of degradation, coloring, and lens shape change due to moisture absorption.

  When forming a microlens, a photosensitivity usually containing an alkali-soluble resin and / or a precursor of these alkali-soluble resins as described above, a photosensitive component, and, if necessary, a curing agent or a sensitizer. A resin composition is used. For example, alkali-soluble resins and / or precursors of these alkali-soluble resins and photosensitive components such as quinonediazide compounds, photosensitive components such as photoacid generators and photobase generators, alkali-soluble resins and / or Or the thing containing the precursor of these alkali-soluble resins, the thing containing the precursor of an alkali-soluble resin and / or these alkali-soluble resins, a photopolymerizable monomer, and a photoinitiator, etc. can be illustrated. These photosensitive resin compositions may contain other components such as a sensitizer and a curing agent as necessary.

  A method for forming the microlens is not particularly limited, but a gradation exposure method is preferable because a lens having a desired shape can be easily manufactured with high accuracy. Furthermore, the gradation exposure method lowers the post-baking temperature, unlike the heat flow method that forms a curved lens surface, due to the surface tension when the photosensitive resin pattern is heated and melted by post-baking after development. Therefore, there is an advantage that deterioration of the lens material due to heat and damage to the solid-state imaging device substrate and a layer provided thereon can be reduced. In post-baking at a low temperature, for example, when a lens made of polyimide resin is formed, the ratio of remaining unreacted polyamic acid increases, so that the lens deteriorates, colors, and changes in shape in a water-existing environment. However, according to the present invention, water resistance is imparted by the water-repellent layer even in the case of a microlens formed by a gradation exposure method, so that it is colored by contact with water. And deterioration and deformation of the lens shape can be prevented. Therefore, the lens of the present invention is particularly suitable when formed by a gradation exposure method.

Here, an example of a microlens formation method by the gradation exposure method will be described.
First, an imaging device substrate including a silicone wafer 1, a signal transfer unit 2 formed on the silicone wafer 1, and a light receiving unit 3 formed on the surface of the silicone wafer 1 between the signal transfer units 2 is provided. prepare. On the entire surface of the image pickup device substrate, red, green and green are arranged in positions corresponding to the light receiving portion 3 on the lower planarizing film 4 and then the light receiving portion 3 on the lower flattening film 4 according to the spectral characteristics required for each light receiving portion. , Blue (RGB) combination, cyan, magenta, yellow (CMY) combination or other color filter layer 5, and on the color filter layer 5, an upper planarizing film 6 made of resin is formed on the entire surface. Provide (see FIG. 1). These layers can be formed by a general method.

  Next, on this upper planarizing film 6, a photosensitive resin composition for forming a microlens is applied by an arbitrary coating method such as a spin coater, a roll coater, a curtain coater, etc. to form a coating film, Pre-bake under suitable conditions, for example at 70-160 ° C. for 1-10 minutes. The thickness of the coating film of the photosensitive resin composition is such that the film thickness after pre-baking is about 0.3 to 2.0 μm, the shape and size of the lens to be produced, the maximum remaining film ratio of the photosensitive resin composition, etc. May be determined as appropriate. After pre-baking, a lens shape is formed by irradiating light through a photomask for gradation exposure and developing with a developer. After the development, the film is post-baked under suitable conditions, for example, at 170 to 240 ° C. for 3 to 60 minutes.

In the exposure step, it is preferable to perform exposure by a projection exposure method using a stepper in order to perform exposure more precisely. The light beam used for exposure may be appropriately selected from ultraviolet rays having a wavelength in the visible and non-visible regions, electromagnetic waves, and radiation having a wavelength that causes a reaction of a photocurable component. Ultraviolet rays such as h rays and i rays, particularly i rays are preferably used. The exposure amount varies depending on the photosensitive resin composition used, but is usually about 10 to 500 mJ / cm ² . You may provide a heating process after exposure as needed. In the case of a chemically amplified photosensitive resin composition containing a photoacid generator or a photobasic generator, this heating step is usually provided to diffuse the acid or alkali generated by exposure. What is necessary is just to set suitably the heating temperature, heating time, etc. in this heating process.

  In the developing step, the exposed portion is dissolved and developed by an immersion method, a spray method, a paddle method, etc., to obtain a lens having a predetermined shape. A solid-state imaging element lens manufactured using a photomask for gradation exposure heats and heat-heats a photosensitive resin composition patterned into a rectangular shape after development, or etches back a lens material layer. There is no necessity, and a lens shape having a desired shape can be obtained after development. Therefore, a highly accurate microlens can be formed in a shorter process than in the prior art with a high yield.

  The composition of the developer and the development conditions may be appropriately selected according to the photosensitive resin composition to be used. As the developer, the unexposed part (positive type) or the exposed part (negative type) of the photosensitive resin composition is hardly dissolved, and the exposed part (positive type) or the unexposed part (negative type) can be completely dissolved. It goes without saying that things are preferred.

  As the developer, for example, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium oxalate, sodium metasuccinate, aqueous ammonia, ethylamine, diethylamine, dimethylethanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, choline An alkaline aqueous solution prepared by dissolving an alkaline compound such as pyrrole or piperidine so as to have a concentration of 0.001 to 10% by weight, preferably 0.01 to 1% by weight is suitable. When using a developer comprising such an alkaline aqueous solution, it is generally washed with water after development. When the lens material does not have alkali developability, other solutions such as a solvent and a surfactant solution may be used as the developer.

After development, an exposure of about 10 to 2000 mJ / cm ² may be performed as necessary. When a quinonediazide compound is contained, the quinonediazide compound can be decomposed by performing exposure again after development to improve the light (particularly visible light) transmittance of the lens.
A water repellent layer may be formed on the surface of the lens thus obtained by the method described above.

  The solid-state imaging element lens of the present invention formed as described above can be suitably used for a solid-state imaging element such as a CCD element or CMOS, or a small solid-state imaging element for a mobile phone.

Example 1
Photosensitive polyimide CS5100 (manufactured by Toray), which is a lens material, was applied on a glass wafer so that the film thickness after post-baking would be 1 μm, followed by pre-baking and development to produce a flat film. After the photosensitive component was faded by post-exposure with a high-pressure mercury lamp at 500 mJ / cm ² , the formed film was post-baked at 230 ° C. for 5 minutes to be fixed. At this time, the water contact angle on the surface of the flat membrane (10 μl of pure water was dropped and the value after 10 seconds was measured using a CA-Z type manufactured by Kyowa Interface Science Co., Ltd., hereinafter the same) was 72 °. It was.

  LR202 (manufactured by Nissan Chemical Industries, Ltd.), which is a silicone-based curable composition, is applied to the surface of the obtained flat film so that the thickness after curing is 100 nm, and cured by baking at 230 ° C. for 15 minutes. Then, a silicone resin water repellent layer was formed. The water contact angle on the surface of the water repellent layer provided on the flat film surface was 108.1 °.

  The transmittance of light at each wavelength in the range of 400 to 750 nm was compared immediately after the flat film with the water-repellent layer formed, and after storage for 1000 hours in an environment of 85 ° C. and 85% RH. As a result, even when the rate of decrease in transmittance was the largest (400 nm), the rate of decrease was only 3%.

Next, on the surface of an imaging device substrate provided with a signal transfer unit and a light receiving unit on a silicone wafer (hereinafter referred to as a silicone wafer substrate) provided with a lower flat lower film, a color filter layer, and an upper flat film. A lens was formed using the same lens material as described above. At this time, coating, development, post-exposure, and baking were performed under the same conditions as for the flat film except that after the lens material coating step, exposure by a defocus method (300 mJ / cm ² ) was performed. Subsequently, a water repellent layer was formed on the lens surface to obtain a solid-state imaging device. As a result of comparing the sensitivity of the obtained solid-state imaging device immediately after forming the water-repellent layer on the lens and after storing for 1000 hours in an environment of 85 ° C. and 85% RH, the sensitivity decreased by only 4%. It was.

(Example 2)
Photosensitive polyimide CS5100 (manufactured by Toray), which is a lens material, was applied on a glass wafer so that the film thickness after post-baking would be 1 μm, followed by pre-baking and development to produce a flat film. After the photosensitive component was faded by post-exposure with a high-pressure mercury lamp at 500 mJ / cm ² , the formed film was post-baked at 230 ° C. for 5 minutes to be fixed. At this time, the water contact angle on the flat film surface was 72 °.

  By applying ARTON (manufactured by JSR), which is an alicyclic resin, to the surface of the obtained flat film so that the thickness after curing becomes 100 nm, and baking at 150 ° C. for 15 minutes, the alicyclic resin repellent property is obtained. An aqueous layer was formed. The water contact angle on the surface of the water repellent layer provided on the flat film surface was 91 °.

  The transmittance of light at each wavelength in the range of 400 to 750 nm was compared immediately after the flat film with the water-repellent layer formed, and after storage for 1000 hours in an environment of 85 ° C. and 85% RH. As a result, even when the rate of decrease in transmittance was the largest (400 nm), the rate of decrease was only 5%.

Next, a lens was formed on the surface of the silicon wafer substrate using the same lens material as described above. At this time, coating, development, post-exposure, and baking were performed under the same conditions as for the flat film except that after the lens material coating step, exposure by a defocus method (300 mJ / cm ² ) was performed. Subsequently, a water repellent layer was formed on the lens surface in the same manner as described above to obtain a solid-state imaging device. As a result of comparing the sensitivity of the obtained solid-state imaging device immediately after forming the water-repellent layer on the lens and after storing for 1000 hours in an environment of 85 ° C. and 85% RH, the sensitivity was reduced by only 5%. .

(Example 3)
Photosensitive polyimide CS5100 (manufactured by Toray), which is a lens material, was applied on a glass wafer so that the film thickness after post-baking would be 1 μm, followed by pre-baking and development to produce a flat film. After the photosensitive component was faded by post-exposure with a high-pressure mercury lamp at 500 mJ / cm ² , the formed film was post-baked at 230 ° C. for 5 minutes to be fixed. At this time, the water contact angle on the flat film surface was 72 °.

As a fluorine-containing curable resin composition, Optool DSX (manufactured by Daikin Industries, Ltd., having a structure in which fluorine is bonded to a silicone skeleton) is applied to the obtained flat film surface so that the thickness after curing is 100 nm. The mixture was heated at 80 ° C. for 5 minutes, and then allowed to stand at room temperature (about 25 ° C.) in the atmosphere for 1 hour or longer to cure to form a fluorine-containing resin water repellent layer. The water contact angle on the surface of the water repellent layer provided on the flat film surface was 113 °.
Further, when OPTOOL DSX (manufactured by Daikin Industries) was vapor-deposited on the flat film surface obtained in the same manner as described above so that the thickness after curing was 100 nm, a water repellent layer having similar characteristics was formed. I was able to.

  The transmittance of light at each wavelength in the range of 400 to 750 nm was compared immediately after the flat film with the water-repellent layer formed, and after storage for 1000 hours in an environment of 85 ° C. and 85% RH. As a result, even when the rate of decrease in transmittance was the largest (400 nm), the rate of decrease was only 4%.

Next, a lens was formed on the surface of the silicon wafer substrate using the same lens material as described above. At this time, coating, development, post-exposure, and baking were performed under the same conditions as for the flat film except that after the lens material coating step, exposure by a defocus method (300 mJ / cm ² ) was performed. Subsequently, a water repellent layer was formed on the lens surface to obtain a solid-state imaging device. As a result of comparing the sensitivity of the obtained solid-state imaging device immediately after forming the water-repellent layer on the lens and after storing for 1000 hours in an environment of 85 ° C. and 85% RH, the sensitivity was reduced by only 5%. .

Example 4
Photosensitive polyimide CS5100 (manufactured by Toray), which is a lens material, was applied on a glass wafer so that the film thickness after post-baking would be 1 μm, followed by pre-baking and development to produce a flat film. After the photosensitive component was faded by post-exposure with a high-pressure mercury lamp at 500 mJ / cm ² , the formed film was post-baked at 180 ° C. for 15 minutes to be fixed. At this point, the water contact angle on the flat film surface was 74 °.

Optool DSX (manufactured by Daikin Industries) as a fluorine-containing curable resin composition was applied to the obtained flat film surface so that the cured film had a thickness of 100 nm, followed by heating at 80 ° C. for 5 minutes, The film was allowed to stand at room temperature (about 25 ° C.) for 1 hour or longer to cure to form a fluorine-containing resin water-repellent layer. The water contact angle on the surface of the water repellent layer provided on the flat film surface was 113 °.
Further, when OPTOOL DSX (manufactured by Daikin Industries) was vapor-deposited on the flat film surface obtained in the same manner as described above so that the thickness after curing was 100 nm, a water repellent layer having similar characteristics was formed. I was able to.

  The transmittance of light at each wavelength in the range of 400 to 750 nm was compared immediately after the flat film with the water-repellent layer formed, and after storage for 1000 hours in an environment of 85 ° C. and 85% RH. As a result, even when the rate of decrease in transmittance was the largest (400 nm), the rate of decrease was only 5%.

Next, a lens was formed on the surface of the silicon wafer substrate using the same lens material as described above. At this time, coating, development, post-exposure, and baking were performed under the same conditions as for the flat film except that exposure by a gradation exposure method (300 mJ / cm ² ) was performed after the lens material coating step. Subsequently, a water repellent layer was formed on the lens surface to obtain a solid-state imaging device. As a result of comparing the sensitivity of the obtained solid-state imaging device immediately after forming the water-repellent layer on the lens and after storage for 1000 hours in an environment of 85 ° C. and 85% RH, the sensitivity was reduced by only 6%. .

(Example 5)
MFR401 (manufactured by JSR) containing a lens material, parahydroxystyrene resin and epoxy resin, which generates a phenol ester after curing, is applied on a glass wafer so that the film thickness after post-baking is 1 μm, followed by pre-baking. Development was performed to produce a flat film. After the photosensitive component was faded by post-exposure with a high-pressure mercury lamp at 500 mJ / cm ² , the formed film was post-baked at 230 ° C. for 5 minutes to be fixed. At this time, the water contact angle on the flat film surface was 67 °.

Optool DSX (manufactured by Daikin Industries) as a fluorine-containing curable resin composition was applied to the obtained flat film surface so that the thickness after curing was 100 nm, followed by heating at 80 ° C. for 5 minutes, and then room temperature ( (About 25 ° C.) It was allowed to stand for 1 hour or longer in the atmosphere and cured to form a fluorine-containing resin water-repellent layer. The water contact angle on the surface of the water repellent layer provided on the flat film surface was 113 °.
Further, when OPTOOL DSX (manufactured by Daikin Industries) was vapor-deposited on the flat film surface obtained in the same manner as described above so that the thickness after curing was 100 nm, a water repellent layer having similar characteristics was formed. I was able to.

  The transmittance of light at each wavelength in the range of 400 to 750 nm was compared immediately after the flat film with the water-repellent layer formed, and after storage for 1000 hours in an environment of 85 ° C. and 85% RH. As a result, even when the rate of decrease in transmittance was the largest (400 nm), the rate of decrease was only 3%.

Next, a lens was formed on the surface of the silicon wafer substrate using the same lens material as described above. At this time, coating, development, post-exposure, and baking were performed under the same conditions as for the flat film except that after the lens material coating step, exposure by a defocus method (300 mJ / cm ² ) was performed. Subsequently, a water repellent layer was formed on the lens surface to obtain a solid-state imaging device. In the obtained solid-state imaging device, as a result of comparing the sensitivity immediately after forming the water repellent layer on the lens and after being stored for 1000 hours in an environment of 85 ° C. and 85% RH, the sensitivity was reduced by only 4%. .

(Comparative Example 1)
The same evaluation as in Example 1 was performed except that the water repellent layer was not formed.
The water contact angle in the flat film was 72 °. Moreover, as a result of comparing the transmittance of light at each wavelength in the range of 400 to 750 nm after storage for 1000 hours in an environment of 85 ° C. and 85% RH immediately after the production of the flat film, the rate of decrease in transmittance was the highest. When it was large (400 nm), the rate of decrease was 10%.

Next, a lens was formed on the silicone wafer substrate using the same lens material as described above to obtain a solid-state imaging device. At this time, coating, development, post-exposure, and baking were performed under the same conditions as for the flat film except that after the lens material coating step, exposure by a defocus method (300 mJ / cm ² ) was performed. As a result of comparing the sensitivity of the obtained solid-state imaging device immediately after lens production and after storage for 1000 hours in an environment of 85 ° C. and 85% RH, a sensitivity reduction of 11% occurred.

(Comparative Example 2)
The same evaluation as in Example 4 was performed except that the water repellent layer was not formed.
The water contact angle in the flat film was 74 °. Moreover, as a result of comparing the transmittance of light at each wavelength in the range of 400 to 750 nm after storage for 1000 hours in an environment of 85 ° C. and 85% RH immediately after the production of the flat film, the rate of decrease in transmittance was the highest. When large (400 nm), the rate of decrease was 14%.

Next, a lens was formed on the surface of the silicone wafer substrate using the same lens material as described above to obtain a solid-state imaging device. At this time, coating, development, post-exposure, and baking were performed under the same conditions as for the flat film except that exposure by a gradation exposure method (300 mJ / cm ² ) was performed after the lens material coating step. As a result of comparing the sensitivity of the obtained solid-state imaging device immediately after lens production and after storage for 1000 hours in an environment of 85 ° C. and 85% RH, the sensitivity was reduced by 16%.

(Comparative Example 3)
The same evaluation as in Example 5 was performed except that the water repellent layer was not formed.
The water contact angle in the flat film was 66 °. Moreover, as a result of comparing the transmittance of light at each wavelength in the range of 400 to 750 nm after storage for 1000 hours in an environment of 85 ° C. and 85% RH immediately after the production of the flat film, the rate of decrease in transmittance was the highest. When large (400 nm), the rate of decrease was 7%.

Next, a lens was formed on the surface of the silicone wafer substrate using the same lens material as described above to obtain a solid-state imaging device. At this time, coating, development, post-exposure, and baking were performed under the same conditions as for the flat film except that after the lens material coating step, exposure by a defocus method (300 mJ / cm ² ) was performed. As a result of comparing the sensitivity of the obtained solid-state imaging device immediately after lens production and after storage for 1000 hours in an environment of 85 ° C. and 85% RH, the sensitivity was reduced by 9%.

It is a figure which shows the typical structure of a solid-state image sensor. It is a figure explaining the measuring method (droplet method) of the water contact using a contact angle meter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Silicone wafer 2 ... Signal transfer part 3 ... Light-receiving part 4 ... Lower planarizing film 5 (5R, 5G, 5B) ... Color filter layer 6 ... Upper planarizing film 7 ... Lens

Claims (14)

  A microlens that is formed on the light-receiving unit of the solid-state imaging device substrate on which at least the light-receiving unit and the signal transfer unit are formed and collects light on the light-receiving unit, and includes a water repellent layer on the surface of the microlens A lens for a solid-state imaging device.   The lens for a solid-state imaging device according to claim 1, wherein the water repellent layer is provided on the outermost surface of the microlens.   The lens for a solid-state imaging device according to claim 1, wherein the water repellent layer contains a water repellent resin as a component that imparts water repellency.   The lens for a solid-state imaging element according to claim 1, wherein the water-repellent resin is an alicyclic resin and / or a silicone-based resin.   The lens for a solid-state imaging device according to any one of claims 1 to 4, wherein the water-repellent resin is a fluorine-containing resin.   The solid-state imaging element lens according to claim 1, wherein the microlens contains a hydrolyzable material.   7. The solid-state imaging device according to claim 1, wherein when the water repellent layer has a film thickness of 50 nm to 500 nm, light transmittance at each wavelength in the range of 400 to 750 nm is 95% or more. lens.   A water repellent coating material for a solid-state imaging element lens, comprising a water repellent resin and / or a water repellent resin precursor.   The water-repellent coating material for a solid-state imaging element lens according to claim 8, wherein the water-repellent resin includes an alicyclic resin and / or a silicone-based resin.   The water repellent coating material for a solid-state imaging element lens according to claim 8 or 9, wherein the water repellent resin precursor includes an alicyclic resin precursor and / or a silicone resin precursor.   The coating material for a solid-state imaging element lens according to claim 8, wherein the water repellent resin contains a fluorine-containing resin.   The water repellent coating material for a solid-state imaging element lens according to claim 8, wherein the water repellent resin precursor includes a fluorine-containing resin precursor.   The solid-state imaging element lens according to any one of claims 8 to 12, wherein when formed into a solidified or cured film having a thickness of 50 nm to 500 nm, the light transmittance at each wavelength in the range of 400 to 750 nm is 95% or more. Water repellent coating material. In the solid-state imaging device, comprising at least a solid-state imaging device substrate on which a light-receiving unit and a signal transfer unit are formed, and a microlens formed on the light-receiving unit of the solid-state imaging device substrate and condensing on the light-receiving unit. A solid-state imaging device comprising a water repellent layer on a surface of a lens.

Images