JP2008224700A - Method for manufacturing liquid crystal optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a highly reliable liquid crystal optical element, which prevents a seal from being eluted into a liquid crystal even when the liquid crystal optical element is manufactured by an ODF process and improves adhesion between a UV-curable seal and a substrate. <P>SOLUTION: The manufacturing method comprises: a band pass filter forming process for arranging a band pass filter on one surface of a first transparent substrate; a seal forming process for forming a UV-curable seal in a closed ring shape; a seal temporary curing process for temporarily curing a first seal area including a face where the seal is brought into contact with the other face and a second seal area including the inside wall surface of the seal by irradiating the seal with ultraviolet rays from one face through the band pass filter; a liquid crystal dropping process for dropping a liquid crystal into the inside area of the seal; and an actual seal curing process for irradiating the seal with ultraviolet rays after bonding a second transparent substrate to the first transparent substrate through the seal with a prescribed gap to actually cure the seal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a liquid crystal optical element, and in particular, even when a liquid crystal optical element is manufactured using an ODF process, the sealing material does not elute into the liquid crystal during the manufacturing process, and an ultraviolet curable seal and a substrate are provided. It is related with the manufacturing method of the liquid crystal optical element which can improve adhesive force.

  As a conventional method for manufacturing a liquid crystal optical element, a manufacturing method is known in which a thermosetting seal having a liquid crystal injection port is formed at least on a transparent substrate and bonded to a counter substrate to form a liquid crystal cell. In this manufacturing method, after that, the liquid crystal injection port of the liquid crystal cell is immersed in the liquid crystal in a vacuum apparatus, and the device is manufactured by injecting the liquid crystal into the cell by capillary action by gradually returning to the atmospheric pressure.

  For this manufacturing method, after forming a closed ring-shaped UV curable seal on a transparent substrate without forming a liquid crystal injection port, and then dropping an appropriate amount of liquid crystal on the inner area of the seal and bonding it with a vacuum device There is a manufacturing method (hereinafter referred to as “ODF process”) in which the ultraviolet curable seal is cured by irradiating with ultraviolet rays. If this ODF process is used, the time required for liquid crystal injection and the total process can be shortened, and a liquid crystal optical element can be manufactured at low cost.

  However, in the ODF process, liquid crystal is dropped on the inner area of the seal when the seal to be used is uncured, so that the liquid crystal directly contacts the uncured seal and the sealing material is eluted into the liquid crystal. There is a case. In particular, when manufacturing a liquid crystal optical element of homogeneous alignment, since the dropped liquid crystal is hydrophilic on the alignment film, it tends to spread quickly, and the time for the liquid crystal to contact the uncured seal is long. Get faster. Thus, if the sealing material is eluted into the liquid crystal, the liquid crystal alignment is disturbed in the vicinity of the seal, and the desired phase modulation may not be performed in that portion.

  An optical pickup device that reads information on an optical disk or writes information on an optical disk by irradiating an optical disk with laser light emitted from a laser light source and condensing reflected light from the optical disk on a light receiving diode. Of liquid crystal optical elements used for correcting spherical aberration, coma aberration, astigmatism, etc. of laser light, and variable focus lenses in camera modules mounted on portable electronic devices, etc. The size is about several millimeters square, which is very small compared with the external size of a liquid crystal optical element used as a normal display device. There is a possibility that the external size of the liquid crystal optical element will be further reduced with the miniaturization of devices such as an optical pickup device and a camera module. As the element becomes smaller, the width of the inner area of the seal of the liquid crystal optical element also becomes narrower, and the time from when the liquid crystal is dropped onto the inner area of the seal until the uncured seal and the liquid crystal come into contact with each other is further shortened. Is expected.

  Therefore, even for liquid crystal optical elements with a small external size, a manufacturing method is proposed in which the ODF process is adopted as a means to solve the above problems, and the liquid crystal is dropped after the outermost surface of the uncured seal is temporarily cured. (See Patent Document 1).

Here, the manufacturing method of the liquid crystal optical element described in Patent Document 1 will be described.
FIG. 7 is a drawing showing a conventional method for manufacturing a liquid crystal optical element. In addition, this figure (a) shows the seal | sticker formation process which forms an ultraviolet curable seal | sticker on a transparent substrate, this figure (b) shows the seal | sticker temporary hardening process which temporarily hardens the surface of this seal | sticker, (C) shows a liquid crystal dropping step of dropping liquid crystal on the inner region of the seal, and FIG. (D) shows a seal main curing step for main curing of the seal.

  First, in the seal formation step shown in FIG. 7A, a seal 112 made of an ultraviolet curable resin is formed in a closed ring shape on the surface of the transparent substrate 111a using screen printing or a dispenser method. The seal 112 contains an initiator that initiates an epoxy or acrylic polymerization reaction by ultraviolet light. The initiator includes a substance in which there is a substance that reacts in a wavelength range from deep ultraviolet to near ultraviolet. Once the initiator has photoreacted, cation or radical polymerization is initiated and the curing reaction of the uncured seal 112 is promoted.

  Next, in the temporary curing step shown in FIG. 7B, an appropriate amount of seal ultraviolet curing light 117 of far ultraviolet rays or near ultraviolet rays is irradiated from the upper direction of this paper. Here, the UV curable seal is temporarily cured only at the outermost periphery of the uncured seal 112, and seal temporary cured portions 113 are formed on the upper surface and side surfaces of the seal.

  Next, in the liquid crystal dropping process shown in FIG. 7C, the liquid crystal 114 is dropped on the inner region of the seal 112.

  Finally, in the seal main curing step shown in FIG. 7 (d), after the transparent substrate 111b is bonded to the transparent substrate 111a via the seal 112, the deep ultraviolet or near ultraviolet seal main curing light 119 is obtained. By irradiating from the surface of the transparent substrate 111a, the seal 112 is completely cured, and the target liquid crystal optical element is completed.

  In the liquid crystal dropping step shown in FIG. 7C, after the liquid crystal 114 is dropped and injected, the liquid crystal comes into contact with the seal temporary hardening portion 113 on the seal side wall, but the surface of the seal 112 is temporarily hardened. Therefore, the uncured seal 112 does not elute into the liquid crystal 114. Therefore, in the liquid crystal optical element manufactured through the seal main curing process of FIG. 7D, the liquid crystal alignment is not disturbed in the vicinity of the seal.

JP-A-6-208097 (pages 7-11, FIG. 1)

  However, the seal pre-cured portion 113 shown in FIGS. 7C and 7D is formed not only on the side surface of the seal 112 but also on the upper end surface. Therefore, when the transparent substrate 111a and the transparent substrate 111b are bonded together in the seal main curing step, the seal temporary curing portion 113 comes into contact with the surface of the transparent substrate 111b. The temporarily cured seal 112 is effective against contamination of the liquid crystal 114, but extremely reduces the adhesion between the uncured seal 112 and the transparent substrate 111b.

  The decrease in the adhesion between the seal 112 and the transparent substrate 111b is caused by external air contamination and liquid crystal due to deformation / thermal expansion of the substrate and expansion / contraction of the liquid crystal 114 injected into the interior in response to environmental changes such as temperature and humidity. 114 causes a phenomenon such as outflow. This is not preferable in terms of reliability as a liquid crystal optical element and causes a decrease in quality.

  Therefore, even if the liquid crystal optical element is manufactured using the ODF process, the object of the present invention is to improve the adhesion between the ultraviolet curable seal and the substrate without the sealing material eluting into the liquid crystal during the manufacturing process. Another object of the present invention is to provide a method for manufacturing a highly reliable liquid crystal optical element.

In order to achieve the above object, the manufacturing method of the present invention basically adopts the following configuration.
The method of manufacturing a liquid crystal optical element according to the present invention includes a bandpass filter forming step in which a bandpass filter that attenuates and emits the amount of incident ultraviolet light is disposed on one surface of the first transparent substrate; A seal forming step of providing a ring-shaped, ultraviolet-curing seal on the other surface of the transparent substrate, and a surface that is irradiated with ultraviolet light from one surface through a band-pass filter so that the seal is in contact with the other surface. A first seal region, a seal pre-curing step for pre-curing the second seal region including the inner wall surface of the seal, a liquid crystal dropping step for dripping liquid crystal in the inner region of the seal, and a seal with a predetermined gap After the second transparent substrate is pasted to the first transparent substrate via UV, a seal main curing step is performed in which the seal is fully cured by irradiation with ultraviolet rays.

  In the method for manufacturing a liquid crystal optical element of the present invention, the first seal seal step and the second seal step are performed while the third seal region facing the first seal region in the seal remains uncured. This is a step of temporarily curing the region.

  The method for producing a liquid crystal optical element of the present invention is characterized in that the wavelength band of the ultraviolet light described above is in the near ultraviolet region.

  According to the present invention, when a liquid crystal optical element having a small outer size is produced by an ODF process, a highly reliable liquid crystal optical element is formed which prevents elution from the seal to the liquid crystal and improves the adhesion between the substrate and the seal. It becomes possible to do.

  The method for producing a liquid crystal optical element according to the present invention includes a bandpass filter forming step of forming a bandpass filter on one transparent substrate, and a ring-shaped UV curable type on the surface opposite to the surface on which the bandpass filter is formed. A seal forming step for forming a seal, and a seal temporary curing step for temporarily curing the seal. In addition, this manufacturing method includes a liquid crystal dropping step of dropping liquid crystal on the inner region of the temporarily cured seal, and a seal main curing step of permanently curing the seal after the other transparent substrate is bonded through the seal. Have In addition, the characteristic part of the manufacturing method of the present invention is in the technique of pre-curing the seal in the seal pre-curing process and the part to be pre-cured. It will be possible to prevent elution of.

Here, the manufacturing method of the liquid crystal optical element of the present invention will be described.
FIG. 1 is a view showing a manufacturing method of the present invention, FIG. 1 (a) is a view showing a band-pass filter forming step, and FIG. 1 (b) is a view showing a seal forming step. FIG. (C) is a figure which shows a seal | sticker temporary hardening process. FIG. 2 is a drawing showing a manufacturing process subsequent to FIG. 1A, FIGS. 2D and 2E are views showing a liquid crystal dropping process, and FIG. 2F is a seal book. It is a figure which shows a hardening process. In FIG. 1A, 1b represents a transparent substrate, 2b represents a transparent conductive film formed on the transparent substrate, and 3b represents an alignment film formed on the transparent conductive film.

  A band-pass filter 4 having a function of attenuating the amount of ultraviolet light is formed on one surface of the transparent substrate 1b by a sputtering method, a vapor deposition method, a CVD method, or the like by the band-pass filter forming step shown in FIG. Alternatively, a film having the above function is attached to form. The bandpass filter 4 is a dielectric multilayer film provided by laminating SiO2 / TiO2, for example. Details of the function of the bandpass filter 4 will be described later.

Next, after forming a transparent conductive film 2b and an alignment film 3b on the other surface of the transparent substrate 1b,
The alignment film 3b is rubbed so that the alignment of liquid crystal to be injected later (for example, homogeneous alignment) is determined. As the alignment film 3b used here, an inorganic alignment film such as polyimide or SiO can be used.

  Next, in the seal forming step shown in FIG. 1B, a ring-shaped, ultraviolet curable seal 5 is formed on the surface of the alignment film 3b (the other surface of the transparent substrate 1b) by a dispenser coating method or a printing method. To do.

Next, in the seal pre-curing step shown in FIG. 1 (c), the seal pre-curing light 7 in the far-ultraviolet or near-ultraviolet wavelength band for seal pre-curing from the bandpass filter 4 side through the transparent substrate 1b. Is set to a light amount of 200 to 300 mJ / cm ² and irradiated. Here, the light quantity of the seal temporary curing light 7 is attenuated by the band-pass filter 4, and the attenuated ultraviolet light is applied to the uncured seal 5.

  In this way, light absorption of the photopolymerization initiator present in the seal 5 is triggered by the pre-curing reaction, and the photoreaction is started from the side surface and the lower portion of the seal 5 by irradiation of the ultraviolet light from the bandpass filter 4 side. Thus, the seal pre-curing portion 6 is provided on the first seal region on the lower surface of the seal (the surface of the seal 5 facing the transparent substrate 1b) and on the second seal region on the seal side surfaces (the inner wall surface and the outer wall surface of the seal 5). Can be formed.

  Next, the liquid crystal dropping step shown in FIGS. 2 (d) and 2 (e) is performed. FIG. 2D shows a state immediately after the liquid crystal 8 is dropped on the inner region of the ring-shaped seal 5 by the ODF process. In FIG. The state which spreads to the vicinity and is in contact with the seal temporary hardening part 6 of the seal 5 is shown.

  The liquid crystal 8 dropped on the inner region of the seal 5 exists in the form of droplets on the alignment film 3b as shown in FIG. Since the alignment film 3b has been subjected to the alignment treatment described above, the liquid crystal 8 made of nematic liquid crystal is in a homogeneous alignment or a homeotropic alignment.

  When this alignment state is homeotropic alignment, the alignment film 3b and the liquid crystal 8 are hydrophobic, so that the droplet shape can be maintained as shown in FIG. The possibility of contact with is reduced. On the other hand, in the case of the homogeneous alignment, the alignment film 3b and the liquid crystal 8 become hydrophilic, so that the liquid droplet 8 spreads quickly after the liquid crystal 8 is dropped, and the liquid crystal 8 shown in FIG. It will be in the state. In particular, in the case of a liquid crystal optical element having a small outer size, the time until the spread liquid crystal 8 reaches the seal 5 is shortened as described above.

  As described above, since the inner wall surface of the seal 5 is the seal temporary curing portion 6, the sealing material does not elute into the liquid crystal 8 even if the liquid crystal 8 and the seal temporary curing portion 6 come into contact with each other.

Next, the transparent substrate 1b in which the liquid crystal 8 is dropped on the inner region of the seal 5 and the transparent substrate 1a in which the transparent conductive film 2a and the alignment film 3a are formed on one side by the seal main curing step shown in FIG. Are stacked in a vacuum state of about 1 Pa through the seal 5 and then returned to the atmospheric pressure to compress the transparent substrates 1a and 1b to form a predetermined inter-substrate gap. After that, the main curing light 9 in the far ultraviolet or near ultraviolet wavelength band of about ² to 3 J / cm ^{2 is} irradiated from the outer surface of the transparent substrate 1a, so that the polymer formed in the seal is sufficiently radically polymerized or cationic. The transparent substrates 1a and 1b are firmly bonded and fixed by the seal 5 which has undergone polymerization and is cured by crosslinking.

Here, the liquid crystal optical element manufactured by the manufacturing method of the present invention is shown again. FIG. 3A shows a cross-sectional view of the liquid crystal optical element produced through the steps shown in FIGS. 1 and 2, and FIG. 3B shows a top view thereof.

  As described above, through the series of manufacturing steps of the present invention, the liquid crystal 8 is provided in the gap between the transparent substrates 1a and 1b arranged with the transparent conductive films 2a and 2b and the alignment films 3a and 3b facing inward. The target liquid crystal optical element 105 can be obtained in which the bandpass filter 4 is provided on the outer surface of the transparent substrate 1b and the transparent substrates 1a and 1b are firmly held by the ring-shaped seal 5.

  In the band-pass filter forming step shown in FIG. 1A, when the film-like band-pass filter 4 is formed by attaching a transparent substrate, this filter is not particularly necessary as a function of the completed element. If so, it may be peeled off from the element when a series of manufacturing steps is completed. Further, when the band-pass filter 4 is a dielectric multilayer film, this film can be left as it is to function as an antireflection film for the liquid crystal optical element 105. In that case, it is desirable to provide a band-pass filter also on the outer surface of the transparent substrate 1a.

  Next, a preferable function of the bandpass filter 4 used in the manufacturing method of the present invention will be described. FIG. 4A shows the transmittance wavelength dependency of the band-pass filter 4 and the transparent substrate 1b in the liquid crystal optical element 105 according to the present invention described with reference to FIG. 3, and FIG. It is drawing which shows the wavelength dependence of the light absorbency of the seal | sticker 5 of the optical element 105. FIG. In FIG. 4A, reference numeral 10 indicates a transmittance curve of the transparent substrate, and reference numeral 11 indicates a transmittance curve of the bandpass filter. In FIG. 4B, reference numeral 12 denotes an absorbance curve of the seal.

  As shown in FIG. 4A, at the ultraviolet wavelength 365 nm of a typical mercury lamp, the transmittance curve 11 of the bandpass filter has a lower transmittance than the transmittance in the transmittance curve 10 of the transparent substrate. Next, the function of the bandpass filter 4 used in the present invention is set. As shown in FIG. 4B, in the absorbance curve 12, the absorbance of the seal near 365 nm is clearly higher than the absorbance of the seal near 408 nm. Therefore, if the band-pass filter 4 having the transmittance curve 11 shown above is used and pre-curing light (for example, 365 nm ultraviolet light) is irradiated toward the seal 5 in the pre-curing process, the seal pre-curing reaction is performed. It can be seen that the amount of light irradiation for causing the phenomenon can be easily controlled.

  The wavelength band of the ultraviolet light used in the present invention is not limited to this 365 nm, but the above relationship (the transmittance curve 11 of the bandpass filter has a lower transmittance than the transmittance in the transmittance curve 10 of the transparent substrate). Relationship). For example, the near-ultraviolet wavelength 408 nm in a mercury lamp coincides with a blue-violet laser wavelength region (395 to 420 nm) corresponding to the wavelength of laser light oscillated from a laser light source in the optical pickup device, and the liquid crystal optics used in this optical pickup device The element is required to have high transmittance. Even if the liquid crystal optical element manufactured by the manufacturing method of the present invention is used for such applications, the bandpass filter 4 provided in the liquid crystal optical element is designed to have a high transmittance in the blue-violet laser wavelength region. Therefore, there is no problem even if the liquid crystal optical element is mounted on the optical pickup device with the band-pass filter 4 attached.

  Next, matters to be noted in the manufacturing method of the present invention will be described below. FIG. 5A and FIG. 5B are drawings showing the shape of the seal temporary curing portion formed by the seal temporary curing step.

As shown in FIG. 5 (a), the bandpass filter 4 should irradiate more light than necessary, not use the preferred wavelength shown in FIGS. 4 (a) and 4 (b), or have a bandpass filter. When the seal temporary curing portion 6 proceeds from the surface of the seal 5 to the inside of the seal when it does not have a function, the seal inner wall surface, the first seal region including the seal outer wall surface, and the seal 5 and the transparent substrate 2b The seal temporary curing portion 6 is present not only on the second seal region including the facing surface but also on the upper end surface of the seal 5. In this way, when the seal temporary curing portion 6 exists on the upper end surface of the seal, the bonding area between the other transparent substrate in the seal main curing process and the uncured seal 5 is reduced, and the adhesive strength between both transparent substrates is reduced. It becomes weak. This causes a decrease in environmental resistance (reliability) of the element itself, which is not preferable.

  On the other hand, as shown in FIG. 5 (b), in the seal temporary curing process shown in FIG. 1 (c), the function setting of the band-pass filter 4 is considered in consideration of the matters described using FIG. 4 (a). If the seal temporary curing light 7 is irradiated through the bandpass filter 4 using desired ultraviolet light, the first seal region including the inner wall surface of the seal 5 and the seal 5 are in contact with the transparent substrate 2b. Only the second seal region (the seal region where the seal 5 and the transparent substrate 1b face each other) can be temporarily cured. In this state, unlike the state shown in FIG. 5A, the upper end surface of the seal 5 is in an uncured state, and the other transparent substrate and the seal 5 can be bonded with sufficient adhesion. it can.

  As described above, the characteristics of the band-pass filter 4 are important in forming the seal temporary curing portion 6 shown in FIG. In general, mercury lamps or xenon lamps used for UV lamps have the strongest ultraviolet light intensity around 356 nm and can emit ultraviolet light in a region where the absorbance of the seal is high as shown in FIG. In order to control the pre-curing part 6, it is preferable that the transmission characteristics of the bandpass filter 4 shown in FIG.

  Also, when using light of near-ultraviolet light 408 nm, as shown in FIGS. 4A and 4B, the transmittance of the transparent substrate and the bandpass filter 4 is high, but the absorbance of the seal is low, so The reaction occurs only on the outermost surface. Therefore, if this near-ultraviolet light of 408 nm is used, the form shown in FIG. 5B can be formed without depending on the transmittance of the band-pass filter 4. In consideration of this, it is preferable to carry out with ultraviolet light around 365 nm.

  As described above, as the external size of the liquid crystal optical element is reduced, it is necessary to reduce the seal line width. Therefore, it is very important to control the amount of ultraviolet light in the seal temporary curing process described above.

  Next, an example in which the liquid crystal optical element manufactured according to the present invention is mounted on an optical pickup device will be described. FIG. 6 is a block diagram showing the overall configuration when the liquid crystal optical element 105 formed by the manufacturing method of the present invention is mounted on an optical pickup device.

  The optical pickup device shown in FIG. 6 includes a laser light source 101, a coupling lens 103, a polarization beam splitter 104, a liquid crystal optical element 105 as aberration correction means, a quarter wavelength plate 106, an objective lens 107, a condenser lens 109, a light receiving element. The diode 110 is configured.

  In FIG. 6, laser light 102 emitted from a laser light source 101 is converted into parallel light by a coupling lens 103, passes through a polarization beam splitter 104, and then enters a liquid crystal optical element 105. When passing through the liquid crystal optical element 105, the laser light is modulated by the liquid crystal optical element 105, and aberration correction is possible. Thereafter, the light passes through the quarter-wave plate 106 and is condensed on the disk 108 by the objective lens 107. Then, the laser beam reflected by the disk 108 passes through the objective lens 107 and the quarter wavelength plate 106 again, the optical path is changed by the polarization beam splitter 104, and is condensed on the light receiving diode 110 through the condenser lens 109. Is done.

As described above, the liquid crystal optical element manufactured according to the present invention described above has improved the adhesion between the ultraviolet curable seal and the substrate without the sealing material being eluted into the liquid crystal during the manufacturing process of the ODF process. Since it is a highly reliable liquid crystal optical element, by incorporating it as the optical pickup device shown in FIG. 6, accurate reading and writing of the optical pickup device can be realized stably.

It is a figure which shows the manufacturing process of the liquid crystal optical element which concerns on this invention. It is a figure which shows the continuation of the manufacturing process shown in FIG. It is sectional drawing and a top view which show the structure of the liquid crystal optical element manufactured by this invention. It is a figure which shows the transmittance | permeability curve of the transparent substrate and bandpass filter which are used with the manufacturing method of the liquid crystal optical element of this invention, and a figure which shows the light absorption curve of a sealing agent. It is a figure which shows the state preliminarily hardened by the seal | sticker temporary hardening process of this invention, and the state preliminarily hardened | cured optimally. It is a figure for demonstrating the optical pick-up apparatus which mounted the liquid crystal optical element of this invention. It is a figure for demonstrating the manufacturing process of the conventional liquid crystal optical element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Transparent substrate 2a, 2b Transparent conductive film 3a, 3b Orientation film 4 Band pass filter 5 Seal 6 Seal temporary hardening part 7 Seal temporary hardening light 8 Liquid crystal 9 Seal main hardening light 10, 11 Transmission curve 12 Absorbance curve 101 Semiconductor Laser 102 Laser light 103 Coupling lens 104 Beam splitter 105 Liquid crystal optical element 106 λ / 4 wave plate 107 Objective lens 108 Disc 109 Condensing lens 110 Light receiving diode

Claims (3)

A band-pass filter forming step of arranging a band-pass filter that attenuates and emits incident ultraviolet light on one surface of the first transparent substrate;
A seal forming step of providing a closed ring-shaped UV curable seal on the other surface of the first transparent substrate;
A second seal including a first seal region including a surface where the seal comes into contact with the other surface by irradiating the ultraviolet light from the one surface via the bandpass filter, and an inner wall surface of the seal A seal pre-curing step for pre-curing the region;
A liquid crystal dropping step of dropping liquid crystal on the inner region of the seal;
A seal main curing step in which after the second transparent substrate is bonded to the first transparent substrate through the seal with a predetermined gap, the ultraviolet ray is irradiated to fully cure the seal;
A method for producing a liquid crystal optical element, comprising: The seal pre-curing step is a step of pre-curing the first and second seal regions while the third seal region facing the first seal region in the seal remains uncured. A method for producing a liquid crystal optical element according to claim 1. The method for producing a liquid crystal optical element according to claim 1, wherein a wavelength band of the ultraviolet light is from an ultraviolet region to a near ultraviolet region.

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