JP2004354973A - Manufacturing method of optical low-pass filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an efficient manufacturing method of an optical low-pass filter that can adhere a high polymer film to a birefringent plate with a high production yield without leaving air bubbles in between. <P>SOLUTION: In this manufacturing method of an optical low-pass filter in which a high polymer film 2 is sandwiched between a first hard birefringent plate 1 and a second hard birefringent plate 3, two steps are included. The one is a first affixing step to affix a high polymer film 2 to the first birefringent plate 1, and the other one is a second affixing step to affix the second birefringent plate 3 to the high polymer film 2 by pressing in a vacuum environment after the first affixing step. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an optical low-pass filter, and more particularly to a technique for improving the manufacturing yield of an optical low-pass filter having a structure in which a polymer film is sandwiched between birefringent plates.

  2. Description of the Related Art An imaging device such as a CCD or a CMOS is used in an imaging device such as a digital still camera or a digital video camera. This image sensor converts an optical image into an electric signal by pixels arranged in a matrix at a predetermined pitch, and shoots an image. In such an imaging apparatus, when the spatial frequency of the optical image exceeds １ ／ of the sampling frequency determined by the arrangement pitch of the pixels, a pseudo signal such as moiré is generated to lower the image quality.

  For this reason, in an ordinary imaging device, an optical low-pass filter that suppresses a high-frequency component of the spatial frequency of an optical image is arranged in front of the imaging device. As a structure of this optical low-pass filter, there is generally a three-birefringent plate type and a type in which a phase plate is sandwiched between two birefringent plates, and a quarter-wave plate is sandwiched between two birefringent plates. A high performance vertical addition type structure is known.

  In recent years, it has been proposed to use a polymer film formed by a uniaxial stretching method as a quarter-wave plate. By using a polymer film, it is possible to reduce the thickness and the manufacturing cost. A quartz plate is used as the birefringent plate.

  In manufacturing an optical low-pass filter having a structure in which a polymer film is sandwiched between two quartz plates, a step of bonding the two quartz plates to both surfaces of the polymer film using an adhesive or an adhesive is necessary.

  When bonding a polymer film to a quartz plate, air bubbles may enter between the polymer film and the quartz plate. If air bubbles are present, they cannot be used as an optical element, resulting in a failure and a reduction in manufacturing yield.

  The following Patent Document 1 discloses a technique for preventing bubbles from entering by bonding the quartz plates in a vacuum atmosphere when they are bonded to each other.

JP-A-2003-29035

  However, when pressure bonding is performed in a vacuum atmosphere, air bubbles do not remain and the production yield is improved, but there is a problem that it takes time to reduce the pressure from the atmospheric pressure to a vacuum and the production efficiency is poor. For this reason, it is necessary to minimize the number of steps in a vacuum atmosphere so as not to lower the production efficiency.

  Further, when manufacturing an optical low-pass filter, it is necessary to accurately arrange the optical axes of the two birefringent plates and the polymer film, and it is required to bond them at an accurate position in a vacuum atmosphere. .

  The present invention has been made in view of the above circumstances, and has a production efficiency in which a polymer film can be bonded to a birefringent plate with a high production yield so that no bubbles exist between the polymer film and the birefringent plate. It is an object of the present invention to provide a method for manufacturing an optical low-pass filter with good performance.

  Another object of the present invention is to provide a method for manufacturing an optical low-pass filter that can be bonded at an accurate position in a vacuum atmosphere.

  The present inventor has conducted intensive studies in order to achieve the above object, and as a result, when bonding a hard first birefringent plate and a second birefringent plate to both surfaces of a polymer film, first, the polymer film was first bonded to the first birefringent plate. Performing a first laminating step of laminating the polymer film on the refraction plate and then performing a second laminating step of a second laminating step of laminating the polymer film on the second birefringent plate; In the first laminating step of laminating to the hard plate, the polymer film is laminated while extruding bubbles with, for example, a roller or the like, so that it is possible to laminate so that bubbles do not enter even in the air. It is necessary to perform the second bonding step in a vacuum atmosphere in the second bonding step, the vacuum atmosphere is preferably in the range of 500 Pa to 1 Pa, The by performed under a vacuum atmosphere, while enhancing the production yield, a reduction in the production efficiency has been found that can be minimized.

  In the second bonding step performed in a vacuum atmosphere, the polymer film adhered to the first birefringent plate and the second birefringent plate are spaced apart and opposed to each other. By bringing the two birefringent plates close to each other and pressing them together, the hard plates can be bonded together in a vacuum atmosphere without the presence of bubbles.

  In the second bonding step, as a method of bonding the polymer film bonded to the first birefringent plate and the second birefringent plate at an accurate position in a vacuum atmosphere, the polymer film is vertically moved up and down, On the guide device urged upward, one of the first birefringent plate or the second birefringent plate to which the polymer film is adhered is held, and the lower crimping plate existing below it is held. The first birefringent plate or the second birefringent plate is separated from the other, and the polymer film and the second birefringent plate are arranged to face each other, and the upper pressing plate is lowered to be held by the guide device. One of the first birefringent plate and the second birefringent plate is lowered against the urging force of the guide device to bring the polymer film and the second birefringent plate closer to each other with the upper pressing plate, and the upper pressing plate and the lower It is possible to adopt a method in which the sheet is sandwiched between the side pressure-bonding plates and pressed.

When bonding is performed using an adhesive, bonding can be performed more strongly by heating in addition to pressing.
In this case, the heating temperature is preferably in the range of 30 ° C to 80 ° C.

For this reason, it is possible to bond more firmly by sandwiching and pressing between the heated upper and lower pressure bonding plates.
In this case, the pressing pressure is preferably in the range of 1969600 Pa to 4596000 Pa.

  Further, by applying pressure while heating, bonding can be performed more firmly.

  In addition, by applying pressure while heating the cushioning material between the pressure bonding plate and the birefringent plate, the cushioning material can absorb small irregularities of the birefringent plate or the polymer film, and provide uniform pressure. be able to. Thus, the birefringent plate and the polymer film can be firmly bonded.

  Therefore, a first invention provides a method of manufacturing an optical low-pass filter in which a polymer film is sandwiched between a hard first birefringent plate and a hard second birefringent plate. A first laminating step of laminating a molecular film, and a second laminating step of bonding the second birefringent plate to the polymer film in a vacuum atmosphere after the first laminating step. Provided is a method for manufacturing an optical low-pass filter.

  According to a second invention, in the method for manufacturing an optical low-pass filter according to the first invention, the second bonding step is such that the first birefringent plate bonded to the polymer film and the second After separating the birefringent plate and disposing the polymer film and the second birefringent plate to face each other, the polymer film and the second birefringent plate are brought close to each other, and they are crimped. And a method for manufacturing an optical low-pass filter.

  According to a third invention, in the method for manufacturing an optical low-pass filter according to the first invention, the second bonding step is performed on a guide device which moves up and down in a vacuum atmosphere and is normally urged upward. Holding the one of the first birefringent plate or the second birefringent plate to which the polymer film is attached, and placing the first birefringent plate disposed on a lower pressure plate existing below the first birefringent plate. After the polymer film and the second birefringent plate are arranged to face each other while being separated from the other of the plate or the second birefringent plate, the first crimping plate is lowered to hold the first birefringent plate held by the guide device. Lowering one of the birefringent plate or the second birefringent plate against the urging force of the guide device, bringing the polymer film and the second birefringent plate closer with the upper pressure plate, 1 birefringent plate, the polymer film and the second birefringent plate Serial to provide a manufacturing method of the optical low-pass filter characterized interposed therebetween to crimp between the upper cover and the lower cover.

  According to a fourth aspect of the present invention, in the method for manufacturing an optical low-pass filter according to any one of the first to third aspects, the second bonding step is performed by sandwiching between heated upper and lower pressure bonding plates. Provided is a method for manufacturing an optical low-pass filter.

  According to a fifth aspect of the present invention, in the method for manufacturing an optical low-pass filter according to the first aspect, the first bonding step includes bonding the first birefringent plate to the polymer film under a vacuum atmosphere. Provided is a method for manufacturing an optical low-pass filter.

  According to a sixth aspect, in the method for manufacturing an optical low-pass filter according to any one of the first to fifth aspects, a pressure treatment step of applying pressure while heating the optical low-pass filter manufactured in the second bonding step is provided. A method for manufacturing an optical low-pass filter, comprising:

  A seventh invention is directed to the method for manufacturing an optical low-pass filter according to any one of the first to sixth inventions, wherein the vacuum atmosphere is in a range of 500 Pa to 1 Pa. provide.

  According to an eighth aspect of the present invention, in the method for manufacturing an optical low-pass filter according to any one of the first to sixth aspects, the pressure for applying pressure is set in a range of 196,600 Pa to 4,596,000 Pa. I will provide a.

  According to a ninth aspect, in the method for manufacturing an optical low-pass filter according to the fourth aspect, the temperature for heating in the second bonding step is in a range of 30 ° C. to 80 ° C. I will provide a.

  A tenth invention is the method for manufacturing an optical low-pass filter according to any one of the first to sixth inventions, wherein after the first bonding step, the second birefringent plate is placed on the polymer film in a vacuum atmosphere. In the second bonding step of pressing underneath, the bonding is performed by sandwiching a buffer between the lower pressing plate and the birefringent plate, and / or between the upper pressing plate and the birefringent plate. Provided is a method for manufacturing an optical low-pass filter.

  Hereinafter, an embodiment of a method for manufacturing an optical low-pass filter of the present invention will be described, but the present invention is not limited to the following embodiment.

  The optical low-pass filter which is the object of the method for manufacturing the optical low-pass filter of the present invention includes a vertical addition type three-layer structure in which a quarter-wave plate made of a polymer film is sandwiched between two birefringent plates. be able to. As the birefringent plate, a quartz plate having a predetermined crystal plane is usually used. Examples of the polymer film constituting the quarter-wave plate include a uniaxially stretched plastic film. The quarter-wave plate has a function of converting the polarization state of incident light from linearly polarized light to circularly polarized light. A uniaxially stretched polymer film having a predetermined thickness has a property that the birefringence increases as the wavelength of incident light increases. The uniaxially stretched polymer film is, for example, a plastic film having a thickness of about 80 μm. The birefringent plate and the polymer film must be precisely arranged with respect to each other so that the optical axes are in predetermined directions.

  An adhesive or an adhesive is used to attach the birefringent plate to both sides of the polymer film. As the adhesive, a UV-curable adhesive having high production efficiency is usually selected. As the pressure-sensitive adhesive, a type having good light transmittance is selected, and a pressure-sensitive adhesive layer having a thickness of about 20 μm is formed on both surfaces of the polymer film, and the pressure-sensitive adhesive may be supplied in the form of a double-sided pressure-sensitive adhesive tape. In some cases, the pressure-sensitive adhesive layer is formed only on one surface of the polymer film. The surface of the polymer film on which the pressure-sensitive adhesive layer is not provided is bonded with an adhesive.

  FIG. 1 is a flowchart illustrating an example of main manufacturing steps of an optical low-pass filter. The manufacturing process of the optical low-pass filter includes a case in which the first birefringent plate and the second birefringent plate on which the infrared cut film and the antireflection film are formed are bonded together, and a method in which the infrared cut film and the antireflection film are bonded after bonding. In some cases, a film is formed. When bonding using the first birefringent plate and the second birefringent plate on which the infrared cut film and the antireflection film are formed, each of the first birefringent plate and the second birefringent plate has one outer surface side. Next, an infrared cut film forming step and an antireflection film forming step are performed. When an infrared cut film is formed, the birefringent plate may be warped. Therefore, it is preferable to form an infrared cut film and an antireflection film after bonding.

  The normal process is a first laminating process of laminating a polymer film on a first birefringent plate, and then a second laminating process of laminating a polymer film on a first birefringent plate on a second birefringent plate. To manufacture an optical low-pass filter having a three-layer structure. Thereafter, if necessary, a pressure treatment step is performed to further strengthen the bonding by applying pressure while heating the optical low-pass filter. Next, if necessary, an infrared cut film forming step of forming an infrared cut filter on one surface of the optical low-pass filter, and an anti-reflective film forming step of forming an anti-reflective film on the other surface of the optical low-pass filter To add an infrared cut function to the optical low-pass filter and a function of reducing reflection and improving light transmittance. Finally, a cutting step of cutting the optical low-pass filter into a required size is performed. After that, an inspection step and a packing step are performed, and the optical low-pass filter is finally shipped as a product.

  As a method of bonding the polymer film to the first birefringent plate in the first bonding step, the birefringent plate is a hard quartz plate, and the polymer film is soft. By laminating the film with a roller so as to extrude air bubbles, lamination can be performed in the atmosphere. Although the production efficiency is reduced, the first bonding step may be performed in a vacuum atmosphere.

  In the second bonding step in which the polymer film bonded to the first birefringent plate is bonded to the second birefringent plate, it is necessary to bond the hard plates in a vacuum atmosphere in order to bond the hard plates together.

  FIG. 2A is a side perspective view showing a schematic configuration of a vacuum bonding apparatus that can be used in both the first bonding step and the second bonding step.

  2 (b) is an enlarged view of the guide device, FIG. 2 (c) is a plan view showing the positional relationship of the superposition of the first birefringent plate and the polymer film when bonding, and FIG. 2 (d) is FIG. 7 is a side view showing a state in which a pressure bonding operation is performed by a vacuum bonding apparatus.

  As shown in FIG. 2A, the vacuum bonding apparatus 100 includes a vacuum chamber 110, and is connected to a vacuum device (not shown) via a vacuum pipe 111 so that vacuuming can be performed. On the bottom surface in the vacuum chamber 110, a lower pressure plate 121 which is a flat surface plate whose upper surface is finished smoothly is arranged. The lower crimping plate 121 is larger than the first birefringent plate 1, and has a certain margin around the entire first birefringent plate 1 when the first birefringent plate 1 is placed. . A guide device 130 is provided at both ends of the lower pressure bonding plate 121 so as to be able to move up and down vertically through the lower pressure bonding plate 121.

  As shown in the enlarged view of FIG. 2B, the guide device 130 has a wire L-shaped outwardly at the upper end of a lifting pin 131 which is vertically movably held by a lower pressure plate 121. A guide holding portion 132 having a bent shape is provided. The guide holding portion 132 can hold both end edges of the short side 11 of the first birefringent plate 1 having a rectangular shape, and regulate the positions of both side surfaces of the short side 11 from both sides. The elevating pin 131 is urged upward by the elastic member 133, and the guide holding portion 132 is always separated upward from the upper surface of the lower pressure plate 121. By holding the first birefringent plate 1 on the guide holding unit 132, the first birefringent plate 1 can be held in the air. The elevating pin 131 is pushed vertically downward, thereby descending against the urging force of the elastic member 133, and bringing the first birefringent plate 1 held by the guide holding portion 132 into contact with the upper surface of the lower crimping plate 121. It descends to the position. As the elastic member 133, besides the illustrated coil spring, a spring such as a plate spring or a fluid spring or an elastic body such as rubber can be exemplified.

  As shown in FIG. 2C, the width of the polymer film 2 is formed to be slightly smaller than the length of the first birefringent plate 1 and slightly smaller than the separation distance between the lifting pins 131 on both sides. I have. Therefore, as shown in FIG. 2B, the polymer film 2 can be placed on the lower pressure plate 121 between the lifting pins 131.

  An elevating shaft 141 that is driven vertically through a driving device (not shown) through the upper wall of the vacuum chamber 110 is provided, and an upper crimp plate 142 is fixed to a lower end of the elevating shaft 141. The lower surface of the upper pressure plate 142 is parallel to the upper surface of the lower pressure plate 121 and is finished smoothly. The upper crimping plate 142 has substantially the same shape as the lower crimping plate 121, and has a shape and a size that can cover the entire first birefringent plate 1. The drive of the elevating shaft 142 can be lowered to a position where the upper press plate 142 can be pressed by contacting the upper surface of the lower press plate 121 when the upper press plate 142 is lowered.

  A method of performing the first bonding step in a vacuum atmosphere using such a vacuum bonding apparatus 100 will be described with reference to FIG. The polymer film 2 in this case will be described as a type having a pressure-sensitive adhesive layer provided on both surfaces.

  The first birefringent plate 1 and the second birefringent plate 3 are cleaned in advance in a cleaning step, and those whose surface is attached are removed. First, a door (not shown) of the vacuum chamber 110 is opened, and the polymer film 2 with one of the adhesive layers exposed is placed on a predetermined position on the lower pressure plate 121 with the adhesive layer with the exposed adhesive layer facing upward. I do. Next, the first birefringent plate 1 is placed on the guide holding part 132 of the guide device 130. Thereby, the arrangement of the first birefringent plate 1 and the polymer film 2 becomes an overlapping arrangement as shown in FIG. That is, when viewed from above, both ends on the short side 11 side of the first birefringent plate 1 protrude outward from both ends of the polymer film 2. Both edges of the first birefringent plate 1 on the short side 11 side are held by the guide holding portion 132 of the guide device 130, and the first birefringent plate 1 is held in a space above the polymer film 2, And are opposed to each other.

  Next, a door (not shown) of the vacuum chamber 110 is closed to operate a vacuum device (not shown), and the inside of the vacuum chamber 110 is evacuated via a vacuum pipe 111. After the inside of the vacuum chamber 110 reaches a predetermined degree of vacuum, the elevating shaft 141 is driven by a driving device (not shown) to be lowered. As the elevating shaft 141 moves down and the upper pressing plate 142 moves down, it comes into contact with the upper end of the guide holding portion 132, and the upper pressing plate 142 resists the urging force of the elastic member 133 urging the elevating pin 131 upward. Then, the first birefringent plate 1 held by the guide holding unit 132 is lowered while pushing down the guide holding unit 132, and is brought into contact with the polymer film 2 placed on the lower pressure-bonding plate 121. The first birefringent plate 1 is pressed by the upper pressure plate 142 with a predetermined pressure. Thereby, as shown in FIG. 2D, the first birefringent plate 1 and the polymer film 2 are sandwiched between the upper pressure-bonding plate 142 and the lower pressure-bonding plate 121, and pressure-bonded with a predetermined pressure. At this time, the arrangement of the first birefringent plate 1 and the polymer film 2 is kept as shown in FIG. 2C. After crimping for a predetermined time, the drive unit (not shown) is driven to raise the elevating shaft 141 and raise the upper crimp plate 142. As the upper pressure plate 142 rises, the guide holding portion 132 rises by the urging force of the elastic member 133 while holding the first birefringent plate 1 on which the polymer film 2 is bonded, and returns to the original position.

  Next, the vacuum pipe 111 of the vacuum chamber 110 is shut off, the atmosphere is introduced into the vacuum chamber 110, and the pressure is returned to the atmospheric pressure, thereby completing the first bonding step.

  Next, a method of performing the second bonding step using the vacuum bonding apparatus 100 will be described with reference to FIG. FIG. 3A is a plan view illustrating an overlap of the first birefringent plate 1, the polymer film 2, and the second birefringent plate 3, and FIG. 3B shows a state where the first birefringent plate is set on a vacuum bonding apparatus. FIG. 3C is a cross-sectional view showing a state in which pressure bonding is performed.

  First, a door (not shown) of the vacuum chamber 110 is opened to take out the first birefringent plate 1 on which the polymer film 2 is bonded, and as shown in FIG. The refraction plate 3 is placed at a predetermined position. The other pressure-sensitive adhesive layer of the polymer film 2 is exposed, and the first birefringent plate 1 is held again by the guide holding portion 132 of the guide device 130 with the exposed pressure-sensitive adhesive layer facing down. At this time, the first birefringent plate 1, the polymer film 2, and the second birefringent plate 3 are vertically overlapped with each other, as shown in FIG. The second birefringent plate 3 is arranged so as to be orthogonal to the second birefringent plate 3, and the width of the second birefringent plate 3 in the left-right direction on the paper surface is smaller than the width of the polymer film 2 in the same direction. The second birefringent plate 3 placed on the lower pressure plate 121 and the polymer film 2 bonded to the first birefringent plate 1 held by the guide holding portion 132 are spaced apart and opposed to each other. Has been arranged.

  In the arrangement state shown in FIG. 3B, the inside of the vacuum chamber 110 is evacuated through the vacuum pipe 111, and after reaching a predetermined degree of vacuum, the lifting / lowering shaft 141 is driven by a driving device (not shown) to be lowered. When the upper pressing plate 142 descends, it comes into contact with the upper end of the guide holding portion 132, and the upper pressing plate 142 resists the urging force of the elastic member 133 that urges the elevating pin 131 upward. The polymer film 2 attached to the first birefringent plate 1 held by the guide holding portion 132 is moved downward while pressing down the second birefringent plate 3 placed on the lower pressure bonding plate 121. After the contact, the upper birefringent plate 142 presses the first birefringent plate 1 with a predetermined pressure.

  Thereby, as shown in FIG. 3C, the first birefringent plate 1, the polymer film 2 and the second birefringent plate 3 are not illustrated between the upper pressing plate 142 and the lower pressing plate 121. Pressing is performed with a predetermined pressure via an elevating shaft 141 that transmits the driving force of the driving device.

  After crimping for a predetermined time, the drive unit (not shown) is driven to raise the elevating shaft 141 and raise the upper crimp plate 142. As the upper pressure plate 142 rises, the guide holding portion 132 rises while holding the first birefringent plate 1 in which the second birefringent plate 3 is bonded to the polymer film 2 by the urging force of the elastic member 133, and Return to the position. Next, the vacuum pipe 111 of the vacuum chamber 110 is closed, the atmosphere is introduced into the vacuum chamber 110, the pressure is returned to the atmospheric pressure, the door (not shown) of the vacuum chamber 110 is opened, and the first birefringent plates are provided on both sides of the polymer film 2. The optical low-pass filter on which the first and second birefringent plates 3 are bonded is taken out.

  The method of bonding the first birefringent plate 1 and the second birefringent plate 3 on both sides of the polymer film 2 using such a vacuum bonding apparatus 100 is performed in a vacuum atmosphere. The presence of bubbles between the birefringent plates 1 and 3 can be reliably prevented.

  Further, by placing the first birefringent plate 1 on the guide holding portion 132 of the guide device 130, the first birefringent plate 1 can be positioned, and the upper crimping plate is held by the guide holding portion 132. The guide holding portion 132 is vertically pushed down by 142, and the first birefringent plate 1 is lowered to place the polymer film 2 or the second birefringent plate disposed at a predetermined position on the lower lower pressure plate 121. 3 and are accurately superimposed and crimped in a predetermined arrangement. Therefore, the optical axes of the first birefringent plate 1, the polymer film 2, and the second birefringent plate 3 can be accurately arranged in a vacuum atmosphere and bonded together with high accuracy.

  In the description of the second bonding step, the first birefringent plate 1 is held by the guide holding unit 132. However, the second birefringent plate 3 is held by the guide holding unit 132, and the polymer film 2 is bonded. The first birefringent plate 1 may be placed on the lower pressure plate 121.

  In the above description, both the first bonding step and the second bonding step are performed using the vacuum bonding apparatus 100. However, in the present invention, the first bonding step is not performed under a vacuum atmosphere. Therefore, it is preferable in terms of production efficiency that only the second bonding step be performed in a vacuum atmosphere.

  Although the example using the polymer film having the pressure-sensitive adhesive layers on both surfaces is shown, an adhesive may be used. In this case, in order to perform ultraviolet curing, it is preferable that the upper pressure-bonding plate 142 and the lower pressure-bonding plate 121 be made of ultraviolet-transmissive glass or the like, and that an ultraviolet irradiation lamp be disposed in the vacuum chamber 110. . It is also necessary to provide a pre-process for applying the adhesive.

  Further, as shown in FIG. 4, when bonding with an adhesive, it is preferable to incorporate a heating means 150 such as an electric heater in each of the upper pressure plate 142 and the lower pressure plate 121. By heating the pressure-sensitive adhesive with a heating means at the time of pressure bonding, the pressure-sensitive adhesive can be softened to eliminate unevenness on the surface, and the bonding by the pressure-sensitive adhesive can be strengthened.

  Furthermore, the inventor conducted experiments on the conditions for bonding the birefringent plate and the polymer film, such as a vacuum atmosphere (degree of vacuum), a heating temperature (bonding temperature), and a pressing pressure. Have found good conditions for reducing the residual air bubbles on the bonding surface of and improving the production yield. This will be described below.

Table 1 shows the results of measuring the area of bubbles remaining on the bonding surface with respect to a change in the degree of vacuum when the birefringent plate and the polymer film were bonded. The bubble area has a complicated shape, and for convenience, a product of a longitudinal dimension of the bubble and a dimension substantially perpendicular to the length in the longitudinal direction.
Further, as a sample, a birefringent plate having a size of 50 mm × 50 mm and a thickness of 0.7 mm, and a polymer film (thickness) made of polycarbonate having an acrylic pressure-sensitive adhesive layer (thickness of about 20 μm) formed on both surfaces thereof About 80 μm).
As other bonding conditions, the bonding temperature was 40 ° C., the pressing pressure was 196,000 Pa, and the pressing time was 3 minutes. Note that the bonding temperature is the temperature of the birefringent plate and the polymer film to be bonded.

  According to the result, when the degree of vacuum is in the range of 500 Pa to 1 Pa, good bonding conditions in which no air bubbles exist on the bonding surface are obtained.

Next, Table 2 shows the results of measuring the area of bubbles remaining on the bonding surface when the bonding temperature was changed using the same method as in the above-described experiment and using the same sample.
As other bonding conditions, the degree of vacuum was set to 100 Pa, the pressing pressure was set to 196,000 Pa, and the pressing time was set to 3 minutes.

  According to this result, when the bonding temperature is in the range of 30 ° C. to 80 ° C., good bonding conditions in which no air bubbles exist on the bonding surface are obtained.

Further, Table 3 shows the results of measuring the area of the air bubbles remaining on the bonding surface when the pressing force was changed by using the same sample as in the above-described experiment.
As other bonding conditions, the degree of vacuum was 100 Pa, the bonding temperature was 40 ° C., and the pressure bonding time was 3 minutes.

  According to this result, when the pressing pressure is in the range of 1969600 Pa to 4496000 Pa, good bonding conditions in which no air bubbles exist on the bonding surface are obtained.

  Next, another embodiment in the case where the second bonding step is performed using a vacuum bonding apparatus will be described with reference to FIG. FIG. 5A is a plan view illustrating the overlap of the first birefringent plate 1, the polymer film 2, and the second birefringent plate 3, and FIG. 5B shows a state where the first birefringent plate is set on a vacuum bonding apparatus. FIG. 5C is a cross-sectional view showing a state in which pressure bonding is performed.

  First, as shown in FIG. 5B, a buffer 5 is disposed on the upper surface of the lower pressure plate 121, and the second birefringent plate 3 is placed on the buffer 5 at a predetermined position. Examples of the material of the cushioning material 5 include a rubber sheet such as silicone rubber, a foamed product such as polypropylene, polyethylene terephthalate, and urethane, a resin sheet, and paper such as high-quality paper, copy paper, cardboard, and dust-proof paper. The material can be selected from materials softer than metal, such as fibers such as cotton and nylon, and skins such as cowhide.

  Next, the other pressure-sensitive adhesive layer of the polymer film 2 of the first birefringent plate 1 to which the polymer film 2 is bonded is exposed, and the exposed pressure-sensitive adhesive layer is turned down, and the guide holding section 132 of the guide device 130 is exposed. Then, the first birefringent plate 1 is held again. At this time, the first birefringent plate 1, the polymer film 2, and the second birefringent plate 3 vertically overlap each other, as shown in FIG. The second birefringent plate 3 is arranged so as to be orthogonal to the second birefringent plate 3, and the width of the second birefringent plate 3 in the left-right direction on the paper surface is smaller than the width of the polymer film 2 in the same direction. The second birefringent plate 3 placed on the lower pressure plate 121 and the polymer film 2 bonded to the first birefringent plate 1 held by the guide holding portion 132 are separated from each other. They are arranged facing each other.

  In the arrangement state shown in FIG. 5B, the inside of the vacuum chamber 110 is evacuated through the vacuum pipe 111 and reaches a predetermined degree of vacuum. Let it. At this time, when the upper pressing plate 142 descends, it comes into contact with the upper end of the guide holding portion 132, and the upper pressing plate 142 guides and holds against the urging force of the elastic member 133 which urges the elevating pin 131 upward. The polymer film 2 bonded to the first birefringent plate 1 held by the guide holding unit 132 is moved down while pressing down the portion 132, and the second birefringent plate mounted on the lower pressure bonding plate 121. After being brought into contact with 3, the upper birefringent plate 142 presses the first birefringent plate 1 with a predetermined pressure.

  Thereby, as shown in FIG. 5C, the first birefringent plate 1, the polymer film 2 and the second birefringent plate 3 are not illustrated between the upper pressing plate 142 and the lower pressing plate 121. Pressing is performed with a predetermined pressure via an elevating shaft 141 that transmits the driving force of the driving device.

  After crimping for a predetermined time, the drive unit (not shown) is driven to raise the elevating shaft 141 and raise the upper crimp plate 142. As the upper pressure plate 142 rises, the guide holding portion 132 rises while holding the first birefringent plate 1 in which the second birefringent plate 3 is bonded to the polymer film 2 by the urging force of the elastic member 133, and Return to the position. Next, the vacuum pipe 111 of the vacuum chamber 110 is closed, the atmosphere is introduced into the vacuum chamber 110, the pressure is returned to the atmospheric pressure, the door (not shown) of the vacuum chamber 110 is opened, and the first birefringent plates are provided on both sides of the polymer film 2. The optical low-pass filter on which the first and second birefringent plates 3 are bonded is taken out.

Here, the effect of bonding the cushioning material 5 between the second birefringent plate 3 and the lower pressure bonding plate 121 will be described.
The inventor compared the air bubbles remaining on the bonding surface when the cushioning member 5 was arranged between the second birefringent plate 3 and the lower pressure bonding plate 121 and when the cushioning member 5 was not arranged.
Table 4 shows the results of measuring the area of bubbles remaining on the bonding surface when the birefringent plate and the polymer film in the above configuration were bonded together and the pressure bonding time was changed. The bubble area has a complicated shape, and for convenience, a product of the length in the longitudinal direction of the bubble and the length in a direction substantially perpendicular to the longitudinal direction.
Further, as a sample, a birefringent plate having a size of 50 mm × 50 mm and a thickness of 0.7 mm, and a polymer film (thickness) made of polycarbonate having an acrylic pressure-sensitive adhesive layer (thickness of about 20 μm) formed on both surfaces thereof About 80 μm). Dust-proof paper was used as the cushioning material.
As other bonding conditions, the bonding temperature was 40 ° C., the degree of vacuum was 100 Pa, and the pressing pressure was 196,000 Pa.

  According to this result, when the cushioning material was arranged, the compression time was 0.5 minutes or more, and the presence of air bubbles was not confirmed. When the cushioning material was not arranged, the compression time was 3 minutes or more, and the presence of bubbles was not observed. No longer confirmed. This means that the provision of the cushioning material makes it possible to apply a uniform pressing force to the bonding surfaces. For example, when compared with the same pressing time, the pressing can be performed with a uniform pressing force, thereby reducing the presence of bubbles. And the bonding by the adhesive can be further strengthened.

The method of bonding the first birefringent plate 1 and the second birefringent plate 3 on both surfaces of the polymer film 2 using such a vacuum bonding device 100 is performed by bonding in a vacuum atmosphere, By arranging between the birefringent plate 3 and the lower pressure bonding plate 121, it is possible to reliably prevent the presence of bubbles between the polymer film 2 and the birefringent plates 1 and 3.
Note that, in the present embodiment, an example in which the cushioning material is arranged between the lower crimping plate and the birefringent plate has been described. However, the present invention is not limited thereto. A cushioning material may be arranged between the pressure-bonding plate and the birefringent plate.

  The pressing step after the second bonding step is performed to strengthen the bonding when bonding with an adhesive. The pressing step is unnecessary when sufficient bonding strength is obtained in the second bonding step. The pressurization method includes, for example, storing an optical low-pass filter in which birefringent plates 1 and 3 are attached to both sides of a polymer film 2 in an autoclave, introducing high-pressure gas such as compressed air into the autoclave, closing a lid, The heating is performed by a heater built in the autoclave, and the pressure is applied while heating the optical low-pass filter under a high-pressure high-pressure gas and a heated atmosphere. The pressure of the high-pressure gas ranges, for example, from about 0.3 MPa to about 30 MPa, which is the upper limit of the pressure resistance of the autoclave, and the temperature is about 70 to 120 ° C. Alternatively, pressure may be applied while heating using a normal heated pressure bonding plate.

  The reason why the infrared cut filter is formed in the infrared cut film forming step is as follows. That is, the CCD is sensitive to light of a relatively wide wavelength, and has good sensitivity not only to the visible light region but also to the light in the near infrared region (750 to 2500 nm). However, in a normal camera application, an infrared region invisible to human eyes is unnecessary, and when near-infrared light is incident on the image sensor, inconveniences such as a decrease in resolution and unevenness of an image are caused. For this reason, an infrared cut filter such as a colored glass is inserted into an optical system such as a video camera to cut a near infrared ray in incident light. In the optical low-pass filter of the present embodiment, by providing an infrared cut filter, an infrared cut function is added to the optical low-pass filter, and an infrared cut filter as a component is not required, and the number of components is reduced. .

The infrared cut filter includes a high refractive index layer made of a high refractive index dielectric such as TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and a low refractive index layer made of a low refractive index dielectric layer such as SiO ₂ and MgF _2. It has a structure in which several to several tens of refractive index layers are alternately stacked.

  In order to alternately form a high-refractive-index layer and a low-refractive-index layer on a substrate, a physical film-forming method is generally used, and a normal vacuum deposition method is also possible. It is desirable to use ion-assisted vapor deposition, ion plating, or sputtering, which can form a film that can perform controlled control and has little change over time in spectral characteristics due to storage and specification environment changes.

  The vacuum evaporation method is a method in which a thin film material is heated and evaporated in a high vacuum, and the evaporated particles are deposited on a substrate to form a thin film. Ion-assisted vapor deposition is equipped with an ion beam generator and a nutrizer in a vacuum vapor deposition system.The thin film material is vaporized, and the ion beam generator ionizes and accelerates the inert gas or oxygen gas to direct the ion beam to the substrate. This is a method in which the vaporized thin film material is accelerated while the ion beam is uncharged and gasified by a nutrizer, or the thin film material attached to the substrate is activated (mixed) to be activated and deposited. The ion plating method is a method in which vapor deposition particles are ionized and accelerated by an electric field to adhere to a substrate, or a film is formed while activating the substrate with gas ions, and is formed by APS (Advanced Plasma Source), EBEP (Electron). Beam Excited Plasma), RF (Radio Frequency) direct substrate application (reactive vacuum deposition with high-frequency gas plasma generated in a deposition chamber), and the like. The sputtering method is a thin film forming method in which ions accelerated by an electric field collide with the thin film material and the thin film material is sputtered to evaporate the thin film material and deposit evaporated particles on a substrate.

  In a low-pass filter in which a quartz plate is bonded to both surfaces of a polymer film, it is preferable to perform low-temperature film formation at a temperature of 100 ° C. or less because the polymer film and the adhesive are weak to heat.

The antireflection film is composed of a single layer or a multilayer of an inorganic film and an organic film. It may have a multilayer structure of an inorganic coating and an organic coating. The material of the inorganic _{film, SiO 2, SiO, ZrO 2} , TiO 2, TiO, Ti 2 O 3, Ti 2 O 5, Al 2 O 3, Ta 2 O 5, CeO 2, MgO, Y 2 O 3, Inorganic substances such as SnO ₂ , MgF ₂ and WO ₃ can be mentioned, and these can be used alone or in combination of two or more. In the case of a multilayer structure, the outermost layer is preferably made of SiO ₂ .

As the multilayer film of the inorganic coating, the total optical thickness of the ZrO ₂ layer and the SiO ₂ layer from the substrate side is λ / 4, the optical thickness of the ZrO ₂ layer is λ / 4, and the optical thickness of the uppermost SiO ₂ layer is An example is a four-layer structure having a target film thickness of λ / 4. Here, λ is a design wavelength, and usually 520 nm is used.

  As a method for forming the inorganic film, for example, a vacuum deposition method, an ion plating method, a sputtering method, a CVD method, a method of depositing by a chemical reaction in a saturated solution, or the like can be adopted.

  Examples of the material of the organic film include FFP (tetrafluoroethylene-hexafluoropropylene copolymer), PTFE (polytetrafluoroethylene), and ETFE (ethylene-tetrafluoroethylene copolymer). It is selected in consideration of the refractive index. As a film formation method, a film can be formed by a coating method excellent in mass productivity such as a spin coating method and a dip coating method, in addition to a vacuum evaporation method.

  In the method of manufacturing an optical low-pass filter according to the present invention, the step of forming the infrared cut film and the step of forming the antireflection film can be omitted.

(The invention's effect)
ADVANTAGE OF THE INVENTION According to the manufacturing method of the optical low-pass filter of the present invention, the presence of air bubbles between the polymer film and the birefringent plate can be reliably prevented, and the productivity is good.

  Further, according to the method of manufacturing an optical low-pass filter of the present invention, it is possible to perform bonding at an accurate position in a vacuum atmosphere.

It is a flowchart which shows an example of the manufacturing process of the manufacturing method of the optical low-pass filter of this invention. It shows a case where the first bonding step is performed using a vacuum bonding apparatus, in which (a) is a configuration diagram showing an outline of the vacuum bonding apparatus, (b) is an enlarged sectional view showing a guide device, and (c). FIG. 4 is a plan view showing an arrangement relationship of an overlap between a first birefringent plate and a polymer film, and FIG. 4D is a cross-sectional view showing a state where the first birefringent plate and the polymer film are crimped between an upper crimp plate and a lower crimp plate. (A) is a plan view showing an arrangement relationship of an overlap of a first birefringent plate, a polymer film, and a second birefringent plate, and shows a case where a second bonding step is performed using a vacuum bonding apparatus; FIG. 2B is a cross-sectional view showing the vertical arrangement of the first birefringent plate, the polymer film, and the second birefringent plate, and FIG. 2C is a state in which the upper and lower crimping plates are crimped. FIG. It is a schematic block diagram which shows the upper side pressure bonding plate and the lower side pressure bonding plate which each contained the heating means. FIGS. 4A and 4B show another embodiment in which the second laminating step is performed using a vacuum laminating apparatus, and FIG. 4A shows the overlapping arrangement of the first birefringent plate, the polymer film, and the second birefringent plate. (B) is a cross-sectional view showing a vertical arrangement relationship of a first birefringent plate, a polymer film, and a second birefringent plate, and (c) is a sectional view between an upper crimping plate and a lower crimping plate. It is sectional drawing which shows the state which is crimping.

Explanation of reference numerals

  DESCRIPTION OF SYMBOLS 1 ... 1st birefringent plate, 2 ... Polymer film, 3 ... 2nd birefringent plate, 5 ... Buffer material, 100 ... Vacuum bonding apparatus, 110 ... Vacuum chamber, 121 ... Lower crimping plate, 130 ... Guide device Reference numerals 131, lifting pins, 132, guide holding parts, 142, upper crimping plate.

Claims (10)

  In a method for manufacturing an optical low-pass filter in which a polymer film is sandwiched between a hard first birefringent plate and a hard second birefringent plate, a first bonding step of bonding the polymer film to the first birefringent plate A method for manufacturing an optical low-pass filter, comprising: a bonding step; and, after the first bonding step, a second bonding step of pressing the second birefringent plate onto the polymer film in a vacuum atmosphere.   2. The method of manufacturing an optical low-pass filter according to claim 1, wherein the second bonding step separates the first birefringent plate and the second birefringent plate bonded with the polymer film under a vacuum atmosphere. 3. After the polymer film and the second birefringent plate are disposed so as to face each other, the polymer film and the second birefringent plate are brought close to each other, and they are pressed together. Production method.   2. The method for manufacturing an optical low-pass filter according to claim 1, wherein the second bonding step includes: moving the polymer film on a guide device which is vertically moved up and down in a vacuum atmosphere and is normally urged upward. The first birefringent plate or the second birefringent plate is held by holding one of the first birefringent plate or the second birefringent plate, and the first birefringent plate or the second birefringent plate is disposed on a lower pressure plate existing below the first birefringent plate or the second birefringent plate. After the polymer film and the second birefringent plate are arranged opposite to each other while being separated from the other of the refracting plates, the first birefringent plate or the second birefringent plate held by the guide device by lowering the upper pressing plate is lowered. One of the birefringent plates is lowered against the urging force of the guide device, and the polymer film and the second birefringent plate are brought closer to each other by the upper pressing plate, and the first birefringent plate, Compression of the polymer film and the second birefringent plate to the upper side The method for manufacturing an optical low-pass filter, which comprises sandwiching by crimping between the lower cover and.   The method for manufacturing an optical low-pass filter according to any one of claims 1 to 3, wherein the second bonding step is performed by sandwiching and pressing between heated upper and lower pressing plates. .   2. The method for manufacturing an optical low-pass filter according to claim 1, wherein the first bonding step includes bonding the first birefringent plate to the polymer film in a vacuum atmosphere. .   The method for manufacturing an optical low-pass filter according to any one of claims 1 to 5, further comprising a pressure treatment step of applying pressure while heating the optical low-pass filter manufactured in the second bonding step. Manufacturing method of optical low-pass filter.   The method for manufacturing an optical low-pass filter according to any one of claims 1 to 5, wherein the vacuum atmosphere is in a range of 500 Pa to 1 Pa.   The method for manufacturing an optical low-pass filter according to any one of claims 1 to 5, wherein a pressing force for applying pressure is set in a range of 1969600 Pa to 4596000 Pa.   5. The method for manufacturing an optical low-pass filter according to claim 4, wherein the heating temperature in the second bonding step is in a range of 30 ° C. to 80 ° C. The method for manufacturing an optical low-pass filter according to any one of claims 1 to 5, wherein after the first bonding step, the second birefringent plate is pressure-bonded to the polymer film in a vacuum atmosphere. In the bonding step, a method for manufacturing an optical low-pass filter, comprising: pressing a buffer material between a lower pressure-bonding plate and a birefringent plate, and / or between an upper pressure-bonding plate and a birefringent plate; .

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