CN100439973C - optical low pass filter - Google Patents

Abstract

To provide an optical low pass filter capable of achieving excellent optical characteristic when it is assembled in optical equipment such as a video camera or a digital still camera without using a curable adhesive. The optical low pass filter 1 is formed by bonding crystal plates 2 and 3 and a flexible retardation film 4. An adhesion layer 5 in which average thickness of an individual body is 5 to 15[mu]m and thickness difference between the maximum thickness part and the minimum thickness part in the individual body is <=4[mu]m is installed on a bonded surface. When incident wavelength is defined as [lambda], transmitted wave aberration is +-1.5[lambda] or less.

Description

optical low pass filter

technical field

The present invention relates to optical low pass filters.

Background technique

Solid-state imaging elements such as CCD or CMOS are widely used in video cameras and digital still cameras to convert optical images formed by light-receiving lenses into electrical signals for recording. These solid-state imaging devices have a structure in which photodiodes are regularly arranged. Here, when the spatial frequency of the optical image is higher than the sampling frequency determined by the arrangement interval, spurious signals such as moiré will be generated. In order to prevent this spurious signal, an optical low-pass filter using a birefringent plate is disposed between the light receiving lens and the solid-state imaging element. As an optical low-pass filter, a 2-point split type using a single birefringent plate, or a high-performance 4-point split type using a retardation plate or a birefringent plate between 2 birefringent plates can be used.

When constituting such an optical low-pass filter, it is necessary to firmly adhere the birefringent plates or the birefringent plate and the retardation plate without air bubbles. In the past, such a sticking process was performed manually, so the burden on the operator was heavy, and the quality of the product was unstable and could not be stabilized due to variations in the thickness of the adhesive layer due to differences in the operator's proficiency. Provide good products.

Therefore, techniques have been proposed to automate the bonding operation and apply an appropriate amount of adhesive to the optical element to make the thickness of the adhesive layer constant (for example, Patent Document 1). Furthermore, as a technique for improving joint strength, a technique using a cement and a high-melting-point wax (wax) has been proposed.

Patent Document 1 Japanese Patent Application Laid-Open No. 2003-29035

Patent Document 2 Japanese Publication No. 61-28181

However, the techniques of Patent Documents 1 and 2 both use a curing-type adhesive, which cannot solve problems such as the inclusion of air bubbles and the exposure of the uncured adhesive from the joint end to cause poor appearance.

Contents of the invention

Here, it is an object of the present invention to provide an optical low-pass filter that exhibits excellent optical performance when incorporated into optical devices such as video cameras or digital still cameras while eliminating the problems when using a curable adhesive. characteristic.

The optical low-pass filter of the present invention is formed by bonding a plurality of optical elements to each other, and is characterized in that an adhesive layer made of an adhesive is provided on the bonding surfaces of the plurality of optical elements, and , the transmitted wave aberration is ±1.5λ or less (λ is the wavelength of the incident light).

According to the present invention, since an adhesive is used as means for bonding a plurality of optical elements to each other, unlike the case where a curable adhesive is used, bubbles are less likely to be generated in the adhesive layer. In addition, the use of an adhesive prevents misalignment between the optical elements and enables uniform adhesiveness to the bonding surface, so that the joint strength after bonding becomes uniform.

Furthermore, since the transmitted wave aberration of the optical low-pass filter is ±1.5λ or less, the optical characteristics of an optical device incorporating the optical low-pass filter are very excellent. The transmitted wave aberration is preferably ±1.2λ or less, more preferably ±1.0λ or less.

In the present invention, the plurality of optical elements include quartz plates, and an adhesive layer is provided on the bonding surfaces of the quartz plates. Preferably, the average thickness of the individual adhesive layers is 5 μm to 15 μm. The difference between the maximum thickness portion and the minimum thickness portion is 4 μm or less.

According to the present invention, the individual average thickness of the adhesive layer provided on the bonding surfaces of the quartz plates is 5 μm to 15 μm, and the difference between the maximum thickness portion and the minimum thickness portion within the individual is 4 μm or less, so sufficient adhesion can be ensured. Combined strength (bonding strength), and at the same time, the deformation brought to the quartz plate is small, and the transmitted wave aberration can be stably maintained below ±1.5λ.

In the present invention, the plurality of optical elements include a quartz plate and a flexible retardation film, and an adhesive layer is arranged on the bonding surface of the quartz plate and the retardation film, preferably the adhesive layer The average thickness within an individual is 5 μm to 15 μm, and the difference between the maximum thickness portion and the minimum thickness portion within an individual is 4 μm or less.

According to the present invention, the retardation film has flexibility, and it is very easy to stick to the quartz plate. In addition, after bending the retardation film and attaching one end thereof to the quartz plate, the retardation film is returned to a planar shape, and the retardation film is completely attached to the quartz plate, whereby air bubbles can be reliably prevented from entering the adhesive layer. In addition, since the retardation film is used, the weight of the optical low-pass filter can be reduced.

Moreover, the average thickness of the adhesive layer is 5 μm to 15 μm in the individual, and the difference between the maximum thickness part and the minimum thickness part in the individual is 4 μm or less, so sufficient adhesive strength can be ensured, and the retardation film and quartz plate The deformation is small, and the transmitted wave aberration below ±1.5λ can be stably maintained.

In the present invention, it is preferable that the adhesive force of the adhesive layer (based on JIS Z 0237, 180° peel) is 10N/25mm or more.

According to the present invention, since the adhesive force of the adhesive layer is 10 N/25 mm or more, sufficient impact resistance can be exhibited when the optical low-pass filter is attached to a product or when the product is transported. The adhesive force is preferably 15 N/25 mm or more, more preferably 20 N/25 mm or more.

In the present invention, it is preferable that the rolling ball test value (based on JIS Z 0237, J.Dow method) of the adhesive layer is 2 or more.

According to the present invention, since the rolling ball test value of the adhesive layer is 2 or more, when optical elements are bonded together, misalignment can hardly occur. The rolling ball test value is preferably 4 or more.

The optical low-pass filter of the present invention is an optical low-pass filter formed by bonding a plurality of optical elements to each other, and is characterized in that, on the bonding surfaces of the plurality of optical elements, a An adhesive layer, and a silane coupling agent is added to the adhesive.

According to the present invention, since the silane coupling agent is added to the adhesive, the adhesive force at the interface between the plurality of optical elements can be increased, and the adhesive layer can be thinned. As a result, the transmitted wave aberration of the optical low-pass filter can be kept stably at 1.5 μm or less.

Furthermore, when a silane coupling agent is added to the adhesive, the adhesiveness between the plurality of optical elements can be improved. As a result, the moisture resistance and solvent resistance of the optical low-pass filter can be improved.

Description of drawings

FIG. 1 is a schematic cross-sectional view showing the arrangement of an optical low-pass filter according to an embodiment of the present invention.

Fig. 2 is a front view and a cross-sectional view of a first quartz plate of the embodiment.

Fig. 3 is a front view and a cross-sectional view of a second quartz plate of the embodiment.

FIG. 4 is a cross-sectional view of the retardation film of the embodiment.

FIG. 5 is a flowchart of an example of a manufacturing process of the optical low-pass filter of the embodiment.

Fig. 6 is a diagram of a first pasting step in the embodiment.

Fig. 7 is a diagram of a second pasting step in the embodiment.

Symbol Description

1 optical low-pass filter; 2 first quartz plate; 3 second quartz plate; 4 retardation film; 5 adhesive layer.

Detailed ways

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Structure of optical low-pass filter]

FIG. 1 is a schematic cross-sectional view showing main parts of a digital still camera employing a 4-point separation type optical low-pass filter 1 according to the present embodiment.

In FIG. 1 , an optical low-pass filter 1 is disposed between a photoreceiving lens 20 that images incident light and a solid-state imaging element 21 that converts the imaged optical image into an electrical signal for recording.

The light-receiving lens 20 can be one piece, or a plurality of lens groups. Furthermore, the solid-state imaging element 21 can use, for example, a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor).

The solid-state imaging element 21 is disposed on the bottom of a concave package 22 having an opening on the light receiving lens 20 side. Furthermore, in order to prevent dust from adhering to the opening, the opening is covered with a glass cover 23 . Here, in order to prevent the solid-state imaging device 21 from being exposed to radiation such as α-rays, special high-purity glass that does not emit radiation is used for the cover glass 23 .

The optical low-pass filter 1 has a first quartz plate 2 on the solid-state imaging device 21 side, a second quartz plate 3 on the receiving lens 20 side, and a flexible retardation film 4 interposed therebetween. In addition, adhesive layers 5 are respectively provided on the bonding surfaces between the quartz plates 2 and 3 and the phase difference film 4 .

FIG. 2(A) shows a front view of the first quartz plate 2 seen from the light receiving lens 20 side, and FIG. 2(B) shows its cross-sectional view.

The first quartz plate 2 is a quartz plate of the same size as the second quartz plate 3 . The optical axis of the second quartz plate 3 is parallel to the long side of the rectangle (referring to FIG. 2(A)), and on a plane perpendicular to the incident surface, there is an angle of 45° with respect to the normal line of the incident surface (referring to FIG. 2(A) B)).

Here, on the side of the light receiving lens 20 of the second quartz plate 3 and the side of the solid-state imaging element 21 of the first quartz plate 2, anti-reflection films (not shown) for improving the transmittance of visible light are respectively provided.

In addition, instead of the antireflection film, an infrared reflective film that prevents infrared rays from entering the solid-state imaging device 21 may be provided.

FIG. 3(A) shows a front view of the second quartz plate 3 viewed from the light-receiving lens 20 side, and FIG. 3(B) shows a cross-sectional view thereof.

The second quartz plate 3 is a rectangular (25 mm×30 mm) quartz plate with a thickness of 1.322 mm. Its optical axis 30 (the axis in the direction in which birefringence does not occur in birefringent crystals) is parallel to the short side (see FIG. 3(A)), and on a plane perpendicular to the incident surface, it has An angle of 45° (refer to FIG. 3(B)).

In addition, these 1st quartz plate 2 and the 2nd quartz plate 3 are optically identical plates, and mutually rotated 90 degrees about the axis perpendicular|vertical to a quartz plate. In the bonding step described later, using quartz plates of the same structure, bonding was carried out in a state rotated by 90 degrees relative to each other.

The first quartz plate 2 and the second quartz plate 3 use birefringent crystals, that is, high-purity quartz. Examples of such crystals include lithium niobate, sodium saltpetre, calcite, rutile, KDP (KH ₂ PO ₄ ), ADP (NH ₄ H ₂ PO ₄ ), etc. From the viewpoint of strength and cost , preferably quartz.

As shown in FIG. 4 , as the retardation film 4 , a λ/4 plate of a uniaxially stretched polycarbonate synthetic resin film having a thickness of 0.12 mm was used. Here, the phase difference film 4 is pasted on the first quartz plate through the adhesive layer 5 (the average thickness in the individual is 5 μm to 15 μm, respectively, and the difference between the maximum thickness part and the minimum thickness part in the individual is 4 μm or less) that is arranged on both sides. 2 and a second quartz plate 3 for use.

In addition, although not shown, protective films are attached to both surfaces of the adhesive layer 5 , but the protective films are peeled off before the retardation film 4 is attached to the quartz plates 2 and 3 .

As the thermoplastic resin constituting the synthetic resin film functioning as a λ/4 plate, a resin material that develops a phase difference of 0.1 μm to 0.3 μm required for the phase difference film 4 after stretching is used. For example, cellulose-based resins, polystyrene-based resins, vinyl chloride-based resins, polycarbonate-based resins, acrylonitrile-based resins, polyolefin-based resins, polyethersulfone-based resins, polyarylate-based resins, Methyl acrylate resin.

Among them, polycarbonate-based resins have high heat resistance, low water absorption, and are excellent in durability and transparency. Furthermore, by adding a compound having optical anisotropy, it is possible to impart a wavelength dispersion characteristic in which a phase difference increases as the wavelength of incident light increases, and a high-performance λ/4 plate can be formed.

Preferably, the wavelength dispersion characteristic of the phase difference of the synthetic resin film is such that the phase difference increases as the wavelength of the incident light increases. In the range of 0.8μm), the phase difference of λ/4±0.05μm can be achieved.

Such an optical low-pass filter 1 needs to have a transmitted wave aberration of ±1.5λ or less. When the transmitted wave aberration of the optical low-pass filter 1 exceeds ±1.5λ, it will adversely affect the optical characteristics of an optical device (such as a digital still camera) to which the optical low-pass filter 1 is mounted. For example, the image quality after shooting is greatly deteriorated (a straight line or grid shape is slightly deformed, and the line becomes thicker or thinner). Therefore, the transmitted wave aberration is preferably ±1.2λ or less, more preferably ±1.0λ or less.

In addition, for example, the transmitted wave aberration can be measured by measuring the uniformity of parallel planes and measuring the optical thickness using a high-precision laser interferometer type shape measuring machine Verifire series manufactured by ZYGO Corporation.

[Adhesive and adhesive layer]

The adhesive used in the present invention and preferred embodiments of the adhesive layer 5 constituted by the adhesive will be described below.

(type of adhesive)

As the binder, natural rubbers, synthetic rubbers, vinyl acetate/vinyl chloride copolymers, polyvinyl ethers, acryls, modified polyolefins, and the like can be used. Among them, it is preferable to use an acrylic pressure-sensitive adhesive whose main component is alkoxyalkyl acrylate in terms of transparency, adhesiveness, and durability.

(adhesion)

As the adhesive strength of the adhesive, considering the load applied to an optical element such as an optical low-pass filter during product assembly, and the impact during product transportation, the peel strength based on the 180° peel test (based on JIS Z 0237 ) is 10N/25mm or more, particularly preferably 20N/25mm or more.

In addition, the ball tack test (based on JIS Z 0237, J.Dow method) requires an initial adhesive force of at least 2 or more. When pasting, in order to prevent the misalignment of optical elements, preferably 4 above.

(transparency)

Since the adhesive constitutes the light transmission surface of the optical element, high transparency is required. The haze of the optical low-pass filter 1 is preferably 1.0 or less, more preferably 0.5 or less, even more preferably 0.1 or less.

In addition, since the haze may increase due to other factors (for example, the haze may also increase in an optical film made of quartz), the higher the transparency of the adhesive, the better.

Here, the haze is the total haze measured by a method based on JIS K 7105.

(smoothness)

The smoothness of the adhesive layer 5 (the roughness/waviness of the adhesive layer surface when the adhesive is applied to the retardation film 4 ) has a large influence on the transmitted wave aberration of the optical element. If the smoothness is poor, the transmitted wave aberration of the optical element increases, and for example, the optical performance of the digital still camera using the optical low-pass filter 1 deteriorates. Therefore, it is preferable that the smoothness of the adhesive layer 5 is as good as possible.

For example, when applying the adhesive on the retardation film 4 using a roll coater, it is preferable to apply the adhesive (solution) by the following method.

(1) Add a leveling agent to the adhesive solution to reduce the surface tension.

(2) Dry slowly.

a) Reduce coating speed

b) Additional drying gradient

c) Adding a high boiling point solvent.

(3) The viscosity of the coating liquid is increased to such an extent that no coating streaks occur.

(4) The compatibility between the solid content (resin) of the adhesive and the solvent is improved.

(thickness of adhesive layer)

If the adhesive layer 5 is too thick, the above-mentioned smoothness will deteriorate. In addition, there may be cases where the amount of adhesive used increases, overflows on the side of the optical element, and becomes sticky on the side. Also, there is a case where deformation occurs when an external force is applied to a portion where the adhesive excessively functions as a cushioning layer. Conversely, when the adhesive layer 5 is thin, the adhesive force is weak, and there is a possibility that the optical elements may be peeled off due to physical or thermal shock.

However, when the quartz plates 2 and 3 and the retardation film 4 are used as the optical element of the present embodiment, a certain thickness is required to moderate thermal expansion (contraction).

Therefore, it is preferable that the average thickness of the adhesive layer 5 in an individual is 5 μm to 15 μm, and the difference between the maximum thickness portion and the minimum thickness portion in the individual is 4 μm or less, and the average thickness is more preferably 5 μm to 12 μm. The difference between the minimum thickness portion is 4 μm or less, more preferably the average thickness is 5 μm to 10 μm, and the difference between the maximum thickness portion and the minimum thickness portion within an individual is 4 μm or less.

(additive)

Generally, when the adhesive layer becomes thin, the adhesive strength decreases. On the other hand, if a silane coupling agent is added to the adhesive, the adhesive force at the interface between the quartz plate 2 and the retardation film 4 and the adhesive force at the interface between the quartz plate 3 and the retardation film 4 can be improved. Therefore, the adhesive layer can be thinned by adding a silane coupling agent.

As a result, it is easy to keep the transmitted wave aberration of the optical low-pass filter 1 stably at 1.5 μm or less.

Furthermore, when a silane coupling agent is added to the binder, the adhesiveness between the quartz plate 2 and the retardation film 4 and the adhesiveness between the quartz plate 3 and the retardation film 4 can be improved. As a result, the moisture resistance and solvent resistance of the optical low-pass filter 1 can be improved.

As silane coupling agents, there are, for example, γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-methacryloxypropyl Trimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropylmethyldimethoxysilane, vinyltriethoxysilane, vinyltriacetyl Oxysilane, p-trimethoxysilylstyrene, p-triethoxysilylstyrene, p-trimethoxysilyl-α-methylstyrene, p-triethoxysilyl-α -Methylstyrene, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-aminoethyl-3-aminopropylmethyldimethoxysilane, N- 2-aminoethyl-3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N-propyl-3-aminopropyltrimethoxysilane, 4-aminobutyltrimethoxysilane, decyltrimethoxysilane and the like. These silane coupling agents may be used alone or in combination of two or more.

[Manufacturing method of optical low-pass filter]

Next, a method of manufacturing the optical low-pass filter 1 will be described.

(summary of production method)

FIG. 5 is a flowchart showing an example of the manufacturing process of the optical low-pass filter 1 of this embodiment.

As the manufacturing process of this optical low-pass filter 1, there is a case of pasting the first quartz plate 2 and the second quartz plate 3 formed with an infrared cut film and an antireflection film, and there is also a case where the infrared cut film and the antireflection film are formed after pasting. condition of the membrane. When using the first quartz plate 2 and the second quartz plate 3 formed with an infrared cut-off film and an anti-reflection film to paste, on the single surface of the respective outer sides of the first quartz plate 2 and the second quartz plate 3, respectively An infrared cut film forming step and an antireflection film forming step ( S101 , S102 ) are performed. If an infrared cut film is formed, warping may occur on the birefringent plate. Therefore, it is preferable to form an infrared cut film and an antireflection film after pasting.

In this embodiment, after the first pasting step (S103) of pasting the retardation film 4 on the first quartz plate 2, the retardation film 4 pasted on the first quartz plate 2 is pasted to the second quartz plate 3. In the second bonding step above, a mother board for the optical low-pass filter 1 with a three-layer structure is manufactured (S104). Then, if necessary, a pressure treatment step (105) is performed in which the motherboard for the optical low-pass filter 1 is heated and pressurized to make the adhesion more firm. Next, if necessary, an infrared cut film forming step of forming an infrared cut film on one side of the motherboard for the optical low-pass filter 1, and an antireflection film forming step of forming an antireflection film on the other side of the motherboard are carried out. The reflection film forming process ( S106 , S107 ) imparts the function of infrared cutoff to the motherboard, and also adds the function of reducing reflection and increasing light transmittance. Finally, a cutting process (S108) of cutting to a desired size is performed, and then an inspection process and a packaging process are performed, and finally shipped as an optical low-pass filter 1 .

Here, as a method of pasting the phase difference film 4 on the first quartz plate 2 in the first pasting process, since the first quartz plate 2 is hard, the phase difference film 4 has flexibility, so the phase difference film 4 is squeezed using a roller. The phase difference film 4 is pasted on the first quartz plate 2 in the way of air bubbles, so that the pasting can be carried out in the atmosphere. In addition, although the production efficiency will decrease, the first pasting step may be performed in a vacuum atmosphere.

In the second bonding step of bonding the retardation film 4 pasted on the first quartz plate 2 to the second quartz plate 3, since the hard plates are bonded together, the bonding is preferably performed under a vacuum atmosphere.

(Structure of pasting device)

FIG. 6(A) is a side perspective view showing a schematic configuration of a vacuum bonding apparatus 100 that can be used in both the first bonding step and the second bonding step.

Fig. 6 (B) is an enlarged view of the guide device 130, Fig. 6 (C) is a top view of the overlapping positional relationship between the first quartz plate 2 and the retardation film 4 when pasting, and Fig. 6 (D) shows It is a side view of the bonding device 100 in a state of performing a pressing operation.

As shown in FIG. 6(A), this vacuum bonding apparatus 100 has a vacuum chamber 110, is connected to a vacuum device (not shown) by a vacuum pipe 111, and can be vacuumed. On the bottom surface in the vacuum chamber 110, a lower side press plate 121 is arranged, and the lower side press plate 121 is a smooth flat plate whose upper surface is processed to be smooth. The lower pressing plate 121 is larger than the first quartz plate 2 , and its size is such that when the first quartz plate 2 is loaded, it supports the whole of the first quartz plate 2 and has some margin around it. Guide devices 130 are disposed on both ends of the lower pressing plate 121 , and the guiding devices 130 can be vertically raised and lowered through the lower pressing plate 121 .

As shown in the enlarged view of Fig. 6 (B), in the guide device 130, the lifting pin 131 is held on the lower side pressing plate 121, and the lifting pin 131 can be lifted in the vertical direction, and the upper end is provided with a metal wire facing outward. The guide holding portion 132 is bent into an L-shape. The guide holding portion 132 can hold both ends of the short side 2A of the rectangular first quartz plate 2 and regulates the positions of both side surfaces of the short side 2A from both sides. The lift pin 131 is elastically pushed upward by the elastic member 133 , and normally, the guide holding portion 132 is separated upward from the upper surface of the lower pressing plate 121 . By holding the first quartz plate 2 on the guide holding portion 132, the first quartz plate 2 can be held in the air. By vertically pressing down the lift pin 131 , the lift pin 131 is lowered against the spring thrust of the elastic member 133 , and the first quartz plate 2 supported by the guide holder 132 is lowered to a position in contact with the upper surface of the lower pressing plate 121 . As the elastic member 133 , springs such as leaf springs and fluid springs, or elastic bodies such as rubber, can be exemplified besides the illustrated coil springs.

As shown in FIG. 6(C), the width of the phase difference film 4 is formed to be slightly narrower than the length of the first quartz plate 2 and also slightly narrower than the separation distance between the lift pins 131 on both sides. Therefore, as shown in FIG. 6(B) , the retardation film 4 can be placed on the lower press plate 121 between the lift pins 131 .

An elevating shaft 141 is arranged to penetrate the upper wall of the vacuum chamber 110 . The elevating shaft 141 is driven by a driving device not shown to elevate in the vertical direction. An upper pressing plate 142 is fixed to the lower end of the elevating shaft 141 . The lower surface of the upper pressing plate 142 is processed to be smooth in parallel with the upper surface of the lower pressing plate 121 . The upper pressing plate 142 has substantially the same shape as the lower pressing plate 121 , and is formed in a shape and a size capable of covering the entire first quartz plate 2 . The driving of the lifting shaft 141 is set so that when the upper pressing plate 142 is lowered, it can be lowered to a position where it can be brought into contact with the upper surface of the lower pressing plate 121 and can be pressurized.

Next, the important first bonding step and second bonding step in the manufacturing process of the optical low-pass filter 1 will be described in detail.

(first pasting process)

Referring to FIG. 6 , a method of performing the first bonding step in a vacuum atmosphere using the vacuum bonding apparatus 100 will be described. The retardation film 4 in this case is of a type provided with an adhesive layer 5 (with a protective film) on both surfaces.

As the first quartz plate 2 and the second quartz plate 3 , what was previously cleaned in a cleaning step to remove surface deposits was used. First, open the door (not shown) of the vacuum chamber 110, and carry the retardation film 4 with the adhesive layer 5 exposed from the peeling protective film to a predetermined position on the lower side pressing plate 121, and make the exposed adhesive layer 5 face superior. Next, the first quartz plate 2 is placed on the guide holder 132 of the guide device 130 . Thus, the arrangement of the first quartz plate 2 and the retardation film 4 overlaps as shown in FIG. 6(C). That is, both ends of the first quartz plate 2 on the short side 2A side protrude from both ends of the retardation film 4 when viewed from above. Both ends of the short side 2A side of the first quartz plate 2 are supported by the guide holder 132 of the guide device 130, and the first quartz plate 2 is held in the space above the retardation film 4, separated from the retardation film 4, and paired. configuration.

Next, after closing the unillustrated door of the vacuum chamber 110 , the unillustrated vacuum device is operated, and the inside of the vacuum chamber 110 is evacuated through the vacuum pipe 111 . After the inside of the vacuum chamber 110 reaches a predetermined vacuum degree, the lifting shaft 141 is driven to descend by a driving device not shown. The lifting shaft 141 descends, and the upper pressing plate 142 descends, abuts against the upper end of the guide holding portion 132, and resists the elastic thrust of the elastic member 133 that pushes the lifting pin 131 upward, and the upper pressing plate 142 presses the guiding holding portion 132 downward. , lower the first quartz plate 2 held on the guide holder 132 and the retardation film 4 carried on the lower pressing plate 121, and press the first quartz plate with a predetermined pressure with the upper pressing plate 142 2. Thereby, as shown in FIG. 6(D), the first quartz plate 2 and the retardation film 4 are interposed between the upper pressing plate 142 and the lower pressing plate 121, and are pressed at a predetermined pressure. At this time, the overlapping of the first quartz plate 2 and the retardation film 4 is maintained in the arrangement shown in FIG. 6(C) . After the pressing for a predetermined time, a driving device (not shown) is driven to raise the elevating shaft 141 and raise the upper pressing plate 142 . As the upper pressing plate 142 rises, the guide holder 132 rises while supporting the first quartz plate 2 on which the retardation film 4 is pasted by the elastic thrust of the elastic member 133 , and returns to its original position.

Next, the vacuum piping 111 of the vacuum chamber 110 is cut off, the atmosphere is introduced into the vacuum chamber 110, and the pressure is restored to the atmospheric pressure, thereby completing the first bonding step.

(Second pasting process)

Next, a method of performing the second bonding step using the vacuum bonding apparatus 100 will be described with reference to FIG. 7 . Fig. 7(A) is a plan view illustrating the overlapping of the first quartz plate 2, retardation film 4, and second quartz plate 3, and Fig. 7(B) is a cross-sectional view of the state installed on the vacuum bonding apparatus 100 (Fig. 6) , FIG. 7(C) is a cross-sectional view showing the pressed state.

First, open the door not shown in the vacuum chamber 110 (Fig. 6), and take out the first quartz plate 2 pasted with the retardation film 4, as shown in Fig. The position carries the second quartz plate 3 . The protective film is peeled off from the other adhesive layer 5 of the phase difference film 4 to expose the adhesive surface, and the exposed adhesive surface is turned downward, and the first quartz plate 2 is again held on the guide holder 132 of the guide device 130 . The overlapping of the vertical direction of the first quartz plate 2, retardation film 4 and the second quartz plate 3 at this moment is as shown in Figure 7 (A), the first quartz plate 2 of rectangular shape and the second quartz plate of the same rectangular shape 3 are arranged orthogonally, and the width of the second quartz plate 3 in the left-right direction of the paper is narrower than the width of the retardation film 4 in the same direction. The second quartz plate 3 placed on the lower pressing plate 121 is separated from the retardation film 4 pasted on the first quartz plate 2 held on the guide holder 132 , and is arranged as a pair.

As shown in Figure 7(B), the inside of the vacuum chamber 110 is evacuated through the vacuum pipe 111, and after reaching a predetermined degree of vacuum, an unillustrated driving device is driven to lower the lifting shaft 141, and the upper pressing plate 142 Down, abut against the upper end of the guide holder 132, resist the spring thrust of the elastic member 133 that pushes the lift pin 131 upwards, and the upper side pressing plate 142 descends while pressing the guide holder 132 downward, so that it is held on the guide holder. After the retardation film 4 pasted on the first quartz plate 2 on 132 abuts against the second quartz plate 3 carried on the lower pressing plate 121, the upper pressing plate 142 is used to press the first quartz plate 2 with a predetermined pressure. .

Thus, as shown in FIG. 7(C), the first quartz plate 2, the retardation film 4, and the second quartz plate 3 are sandwiched between the upper side pressing plate 142 and the lower side pressing plate 121, and the first quartz plate 2, the phase difference film 4, and the second quartz plate 3 are sandwiched between the upper side pressing plate 142 and the lower side pressing plate 121. The lifting shaft 141 is pressed with a predetermined pressure by the driving force of the driving device.

After the pressing for a predetermined time, a driving device (not shown) is driven to raise the elevating shaft 141 and raise the upper pressing plate 142 . As the upper pressing plate 141 rises, the guide holder 132 rises in the state where the first quartz plate 2 with the second quartz plate 3 attached to the retardation film 4 is supported by the elastic thrust of the elastic member 133, and returns to the original state. s position. Next, close the vacuum piping 111 of the vacuum chamber 110, introduce air into the vacuum chamber 110, return to the atmospheric pressure, open the door (not shown) of the vacuum chamber 110, and take out the first quartz plate 2 and the A laminated plate of the second quartz plate 3 (motherboard for the optical low-pass filter 1).

According to the above-mentioned embodiment, the following effects can be exhibited.

(1) Since an adhesive is used as means for bonding the quartz plates 2 and 3 and the retardation film 4 , unlike the case of using a curable adhesive, bubbles are less likely to be generated in the bonding layer. In addition, since the optical elements are not misaligned by using an adhesive, and the bonding surface has uniform adhesiveness, the bonding strength after bonding can be made uniform. In addition, since the adhesive is coated on the retardation film 4 in advance, excessive adhesive does not overflow to the outside of the optical low-pass filter 1 .

(2) The transmitted wave aberration of the optical low-pass filter 1 is a relatively low value of ±1.5λ or less. Therefore, when the optical low-pass filter is installed in an optical device such as a digital still camera, the Optical properties are very excellent.

(3) In the optical low-pass filter 1, the average thickness of the adhesive layer provided on the bonding surface of the quartz plate and the retardation film is 5 μm to 15 μm in the individual, and the maximum thickness portion and the minimum thickness portion in the individual Since the difference is in the range of 4 μm or less, sufficient adhesive strength (bonding strength) can be ensured, and at the same time, the deformation to the quartz plate is small, and the transmitted wave aberration of ±1.5λ or less can be stably maintained. In addition, if the thickness of the adhesive layer is so thin, the surface of the adhesive layer can be smoothed easily, which is advantageous for stably maintaining the transmitted wave aberration when constituting the optical low-pass filter 1 at ±1.5λ or less.

(4) Since the adhesive layer 5 does not absorb the warpage of the quartz plates 2 and 3, the warpage can be alleviated. As a result, the transmitted wave aberration can be reduced to ±1.5λ or less and stabilized.

(5) Since the retardation film 4 is made of synthetic resin, the weight of the optical low-pass filter 1 can be reduced.

(6) the first quartz plate 2 and the second quartz plate 3 are pasted on both sides of the retardation film 4 in a vacuum atmosphere, therefore, it is possible to more reliably prevent the presence of air bubbles between the retardation film 4 and the quartz plates 2 and 3 .

(7) When the silane coupling agent is contained in the binder, the adhesion between the quartz plates 2 and 3 and the retardation film 4 will be more excellent, and the moisture resistance and solvent resistance will be excellent.

(8) The retardation film 4 is coated with an adhesive in advance and covered with a protective film. Therefore, when the retardation film 4 is attached to the quartz plates 2 and 3, a cleaning step is not required, and contamination of dust and foreign matter is small.

(9) The adhesive elasticity of the adhesive layer 5 absorbs the difference in thermal expansion coefficient between the retardation film 4 and the quartz plates (birefringent plates) 2 and 3 , so that bonding strength against thermal shock can be ensured.

Preferred structures, methods, etc. for carrying out the present invention are disclosed in the above description, but the present invention is not limited thereto. That is, the present invention mainly illustrates and describes specific embodiments, but those skilled in the art can understand the above-mentioned embodiments without departing from the technical idea and purpose of the present invention. Perform various deformations in shape, material, quantity, and other detailed structures.

Therefore, the above-disclosed descriptions that limit the shape, material, etc., are exemplary descriptions made to facilitate understanding of the present invention, and are not intended to limit the present invention, so part of the limitations of these shapes, materials, etc. or the description of the names of all limited components is also included in the present invention.

For example, in the present embodiment, the optical low-pass filter 1 is constituted by the quartz plates 2 and 3 and the retardation film 4 , but the optical low-pass filter may be constituted by using three quartz plates.

And, in the above description, both the first sticking process and the second sticking process are carried out using the vacuum sticking device 100, but in the present invention, the first sticking process can be completed without a vacuum atmosphere, therefore, from the perspective of production efficiency In view of this aspect, it is preferable to perform only the second pasting step in a vacuum atmosphere.

In addition, when pasting with an adhesive, heating units (not shown) such as electric heaters may be built in the upper pressing plate 142 and the lower pressing plate 121 respectively. During pressing, the adhesive is heated by the heating unit to soften the adhesive and smooth the surface, so that the transmitted wave aberration of the obtained optical low-pass filter 1 can be further reduced.

Claims (3)

1. optical low-pass filter, this wave filter is that a plurality of optical elements are pasted the optical low-pass filter that forms each other, it is characterized in that,

Described a plurality of optical element comprises quartz plate;

On described a plurality of optical elements stickup face each other, be provided with the bonding coat that constitutes by bonding agent, and be that the bounding force of the described bonding coat measured of benchmark is more than the 10N/25mm with JIS Z 0237;

The intraindividual average thickness of described bonding coat is 5 μ m～15 μ m, and the difference of intraindividual maximum ga(u)ge portion and minimum thickness portion is below the 4 μ m.

2. optical low-pass filter, this wave filter is that a plurality of optical elements are pasted the optical low-pass filter that forms each other, it is characterized in that,

Described a plurality of optical element comprises quartz plate;

On described a plurality of optical elements stickup face each other, be provided with the bonding coat that constitutes by bonding agent, and be that the roller test value of the described bonding coat measured of benchmark is more than 2 with JIS Z 0237;

The intraindividual average thickness of described bonding coat is 5 μ m～15 μ m, and the difference of intraindividual maximum ga(u)ge portion and minimum thickness portion is below the 4 μ m.

3. optical low-pass filter as claimed in claim 1 or 2 is characterized in that,

Described a plurality of optical element comprises quartz plate and flexual phase retardation film,

The stickup face of described quartz plate and described phase retardation film is provided with bonding coat.

Images