JP2008070678A - Method and apparatus for manufacturing flexible display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently join plastic substrates of flexible display elements together by using laser while suppressing degradation of both the substrates and a display medium to the minimum. <P>SOLUTION: The plastic substrates 10 are joined by mounting the plastic substrates 10 with a photo-curing resin in-between for sealing the display medium such as a liquid crystal on a mounting base 8, by irradiating the photo-curing resin part with laser light 13 of 370nm or more and 450nm or less wavelength through at least one plastic substrate 10 by a moving mechanism 12 moving parallel to the mounting base 8 from a laser head 9 arranged above the mounting base 8. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for manufacturing a flexible display element such as a flexible display or electronic paper, and more particularly to a flexible display element such as a flexible display or electronic paper manufactured by laminating a plastic substrate. The present invention relates to a manufacturing method and an apparatus therefor.

  In recent years, development of new electronic display media incorporating the advantages of paper, such as flexible displays and electronic paper, has been promoted. In addition to the advantages of traditional paper-based media, these electronic display media are highly visible, less tiring, and can be bent for superior portability, and can be rewritten, animated, and combined with digital information. It is expected as an ideal electronic display medium that combines the advantages of electronic displays.

  In particular, electronic paper is expected to realize the advantages of easy viewing and portability of hard copy, as well as combining with digital information of soft copy, rewritability and paper saving resources. The flexible display is a next-generation display that can display moving images and is expected to be a mobile display that can be viewed anywhere, anytime, such as outdoors, or as a lightweight and flexible large display medium. is there.

  There are various operating mechanisms and structures and manufacturing methods corresponding to flexible displays and electronic paper. For example, in flexible liquid crystal displays, a transparent electrode is patterned, and a pair of substrates that have undergone an alignment process are placed inside with an alignment process side. So that the gap is left behind by the spacer, and the periphery of the substrate is bonded to each other with a photocurable resin interposed between them, and the photocurable resin is irradiated with light and cured, and then between the substrates. By filling the liquid crystal, or by interposing a photocurable resin around the substrate, dropping a predetermined amount of liquid crystal onto the substrate, facing the substrate, and irradiating the photocurable resin with light to cure It is manufactured by.

  In addition, the flexible organic EL display has a light emitting layer composed of a multilayer organic film and a back electrode that covers the light emitting layer formed on one substrate on which a transparent electrode is formed, and the other substrate is connected to the organic film and the back surface. Manufactured by interposing a photo-curing resin applied so as to cover the electrodes, facing both substrates so that the element structure such as an organic film is inside, and irradiating the photo-curing resin with light and curing Is done.

  As a method of sealing between glass substrates of a liquid crystal display (LCD) with a sealant, for example, Patent Document 1 describes a method of irradiating a 352 nm XeF excimer laser as a laser. Patent Document 2 describes a method in which a photocurable resin is interposed between a plastic substrate and a glass substrate, and an ultraviolet laser and a laser having an oscillation wavelength of 600 nm or more and 0.1 mm or less are simultaneously irradiated. Yes.

Further, Patent Document 3 describes an exposure apparatus for curing an encapsulant that includes a spatial modulator that spatially modulates an emitted laser and sweeps the laser to selectively irradiate the encapsulant part. Yes.
JP 2003-114442 A JP-A-8-6039 JP-A-11-121166

  However, light of the wavelength described in Patent Document 1 is polyethylene naphthalate (PEN), which is a resin substrate typically used for flexible displays and electronic paper, and polyethylene terephthalate (indium tin oxide (ITO) electrode) ( The transmittance for PET, polyethylene sulfone (PES), etc. is low, and it is not suitable for sealing these substrates. Similarly, the ultraviolet laser described in Patent Document 2 has a problem of transmittance, and cannot be applied to a resin substrate.

  On the other hand, although the encapsulating material curing exposure apparatus described in Patent Document 3 can selectively irradiate the encapsulating material portion, a spatial modulator using a reflective optical system as described is expensive. In addition, since a large space is required above the substrate, the cost of the entire apparatus increases. This problem becomes more pronounced as the substrate size used increases. In addition, the spatial modulator cannot accurately irradiate the sealing material portion even if the optical axis adjustment is slightly shifted, and the optical axis shift due to the vibration of the device or temperature change must be corrected frequently. It can not be said.

  The present invention has been made in view of the above circumstances, and it is possible to bond plastic substrates that are less likely to cause deterioration of substrates, can minimize adverse effects such as deterioration of a display medium, and have low laser energy loss. An object of the present invention is to provide a method for manufacturing a flexible display element and a manufacturing apparatus therefor.

  The present invention relates to a method for manufacturing a flexible display element in which a light-curing resin for sealing a display medium such as a liquid crystal is interposed between plastic substrates, and the plastic substrates are bonded to each other. At least one of the plastic substrates is provided. The laser beam having a wavelength of 370 nm or more and 450 nm or less is irradiated to the photo-curing resin portion, and the plastic substrates are bonded to each other.

  As another aspect, the present invention provides a flexible display element manufacturing method in which a plastic curable resin for sealing a display medium such as a liquid crystal is interposed between plastic substrates and the plastic substrates are bonded to each other. A laser having a wavelength of 370 nm to less than 400 nm and a laser having a wavelength of 400 nm to 450 nm and having a wavelength difference of 20 nm or more are irradiated to the photocurable resin portion simultaneously or before and after through one plastic substrate. The plastic substrates are bonded to each other.

  Here, the photo-curing resin part means that, when a liquid crystal is sealed between plastic substrates and a photo-curing resin is interposed at the edge part, as in a flexible liquid crystal display, An element structure such as an organic film is formed on one substrate as represented by a flexible organic EL display, and the photocurable resin is covered in a wide range so as to cover it. When it is interposed, it indicates the entire area covered by the photocurable resin.

  In addition, the flexible display element means a flexible electronic display element such as a flexible display or electronic paper, and the display medium such as liquid crystal is not limited to the liquid crystal. For example, Microcapsules if the rewriting method is electrophoresis, twist balls if the particles are rotated, liquid crystal if the optical anisotropy, photochromic if the light is absorbed, organic EL if it is self-luminous, flexible display, electronic paper, etc. A display medium widely used in the field.

Irradiation of the laser to the photocurable resin portion means to irradiate the laser to the portion where the photocurable resin exists, but some of the laser from the photocurable resin portion generated at the time of laser irradiation. It is not intended to exclude even protrusions due to deviations or errors.
An example of the plastic substrate is polyethylene naphthalate.

  An apparatus for manufacturing a flexible display element for joining plastic substrates of the present invention places two plastic substrates on which a photocurable resin for sealing a display medium such as a liquid crystal is interposed. A mounting table; a laser head that is provided above the mounting table and emits a laser having a wavelength of 370 nm to 450 nm; and the laser head is mounted on the mounting table as described above so that the laser irradiates the photocurable resin. It comprises a moving mechanism that moves in parallel.

  The laser head preferably emits a laser having a wavelength of 370 nm or more and less than 400 nm and a laser having a wavelength of 400 nm or more and 450 nm or less and having a wavelength difference of 20 nm or more.

  The method for producing a flexible display element of the present invention is a production of a flexible display element in which a plastic substrate is bonded to each other by interposing a photocurable resin for sealing a display medium such as a liquid crystal between plastic substrates. In the method, a laser having a wavelength of 370 nm or more and 450 nm or less having a small absorption by the plastic substrate is irradiated through at least one plastic substrate, so that the plastic substrates can be effectively and efficiently used with laser (energy loss is reduced). Can be bonded while minimizing the deterioration of the plastic substrate.

  The method for producing a flexible display element of the present invention is performed by irradiating a photocurable resin portion with a laser having a wavelength of 370 nm to 450 nm through at least one plastic substrate. As a resin substrate widely used for a flexible display or electronic paper which is an example of a flexible display element, for example, there is polyethylene naphthalate (PEN). The visible light and ultraviolet light transmission characteristics of PEN having a thickness of 100 microns are shown in FIG. In the sealing of a resin substrate using a photocurable resin, in most cases, light is irradiated through one substrate, but when PEN is used for a substrate, even when irradiated with ultraviolet light having a wavelength of 370 nm or less, Since the light intensity is significantly reduced in the resin substrate, it does not reach the photo-curing resin to be cured.

  Some resin substrates used for flexible displays and electronic paper transmit ultraviolet rays up to a wavelength of about 320 nm, such as polyethylene sulfone (PES) and polyethylene terephthalate (PET). It is not used for flexible displays or electronic paper, and is generally sealed in a state where a transparent conductive film or barrier film is coated. The light transmission characteristics of this type of resin substrate coated with a transparent conductive film or a barrier film are typically equivalent to the characteristics of the PEN, and therefore do not transmit ultraviolet light having a wavelength shorter than about 370 nm. In addition, since all ultraviolet rays having a wavelength of 370 nm or less are absorbed by the resin substrate, they do not contribute to the curing of the visible light curable resin (visible light curable adhesive), but also cause yellowing of the resin substrate. It is not preferable. Therefore, the lower limit of the wavelength in the production of the flexible display element of the present invention is 370 nm.

  On the other hand, the absorption wavelength of a photoinitiator contained in a normal ultraviolet curable resin (ultraviolet curable adhesive) is limited to a short wavelength region of 350 nm or less, and does not transmit light in this wavelength region like PEN. Not suitable for sealing substrates. Moreover, since the resin substrate used for a flexible display or electronic paper generally has poor heat resistance, sealing with a thermosetting resin is not appropriate. The visible light curable resin whose absorption wavelength is extended to the visible light region contains a photoinitiator that absorbs visible light and initiates the polymerization reaction of the visible light curable resin. 2 of FIG. 1 shows an absorption spectrum of a visible light curable resin having a thickness of 30 microns.

  When a resin substrate having spectral transmission characteristics such as the above PEN is to be sealed with a visible light curable resin, light in a wavelength region where both of the absorption band and the transmission band overlap with each other must be irradiated. I must. This range is shown as 3 in FIG. 1 as the product of both spectra. The curve shown by 3 in FIG. 1 indicates the effectiveness of the light source wavelength when a flexible display or electronic paper having a resin substrate is sealed with a visible light curable resin, and its range is 370-450 nm. It is. Note that visible light and infrared light having a wavelength of 450 nm or more do not contribute to the curing of the visible light curable resin, but may be absorbed by the element of a flexible display or electronic paper to heat the element and cause deterioration of characteristics. Therefore, the upper limit of the wavelength in the production of the flexible display element of the present invention is 450 nm.

  From the above, the curing light source when sealing a flexible display or electronic paper having a resin substrate with a visible light curable resin must include a spectrum in the wavelength range of at least 370-450 nm. It is preferable that light having a wavelength outside the wavelength range is not included. From such a viewpoint, for example, the emission spectrum of a high-pressure mercury lamp includes light in the range of 370 to 450 nm, but it is not optimal because it also includes light in other wavelength regions. For example, if an optical filter or a multilayer mirror is used, it is possible to extract only light in the range of 370 to 450 nm from the emission spectrum of the high-pressure mercury lamp and irradiate the visible light curable resin. The element is expensive and has a problem that it is easily heated to absorb a part of light, and further its characteristics are easily deteriorated by heat, which is not practical in the application of the present invention. Therefore, the optimum light source is a laser light source or an LED light source having an emission peak in the wavelength range of 370 to 450 nm.

  According to the effective wavelength curve indicated by 3 in FIG. 1, the wavelength at which the visible light curable resin is most efficiently cured is around 405 nm, but the absorption rate of the visible light curable resin at this wavelength is about 405 nm. The remaining 40% of the light reaches the flexible display element and may increase its temperature or deteriorate the characteristics. When the power density of the laser is increased in order to increase the curing speed in the process, 40% of the power reaches the display medium, so that there is an upper limit dependent on the display medium in the irradiation power density. If a desired curing rate cannot be obtained even when 405 nm light is irradiated with an upper limit irradiation power density that does not adversely affect the display medium, a visible light curable type is obtained by simultaneously irradiating light with a shorter wavelength. The total power density absorbed by the resin can be increased.

  The details will be described with reference to FIG. 2 using an example in which a 375 nm laser is used as a shorter wavelength and a 405 nm laser is used as a longer wavelength. FIG. 2 is a partial schematic cross-sectional view of a flexible display sandwiched between two plastic substrates 22 and 22 '. In order to prevent moisture and oxygen from penetrating into the element portion, barrier layers 23 and 23 'are provided inside the two plastic substrates 22 and 22', respectively. In the sealing step, a display medium 24 is manufactured, and a lower plastic substrate 22 covered with a passivation film 25, and an upper plastic substrate 22 ′ in which a photocurable resin layer 26 is applied on the barrier layer 23 ′. And the light for curing is irradiated from the upper plastic substrate 22 'side.

  The thickness of the photocurable resin layer 26 is typically 30 microns. When 405 nm is selected as the irradiation wavelength, the light intensity absorbed by the photocurable resin layer 26 out of the light intensity reaching the upper surface of the photocurable resin layer 26 is about 60%, and 40% is the passivation film 25 and It is absorbed by the display medium 24. On the other hand, when light having a wavelength of 375 nm, which is more strongly absorbed by the photocurable resin layer 26, is irradiated, all of the light that has reached the upper surface of the photocurable resin layer 26 is a portion 27 close to the upper surface of the photocurable resin layer 26. It is absorbed and does not reach the passivation film 25 or the display medium 24. However, since such short-wavelength light is relatively strongly absorbed by the upper plastic substrate 22 ′, the intensity thereof must be suppressed to such an extent that the plastic substrate does not deteriorate in characteristics.

  That is, in the wavelength range of 370 nm to 450 nm, longer wavelength light is not absorbed much by the plastic substrate and contributes to curing over the entire thickness of the photocurable resin layer, but may adversely affect the display medium. Therefore, its strength must be suppressed to such an extent that it does not cause deterioration of the characteristics of the display medium. On the other hand, light having a shorter wavelength does not reach the display medium and contributes to curing near the upper surface of the photocurable resin layer, but may cause deterioration of the characteristics of the plastic substrate. Must be within acceptable limits.

  Therefore, in the sealing process of flexible displays and electronic paper, when trying to maximize the curing rate of the photocurable adhesive, in the wavelength range of 370 nm to 450 nm, the shorter wavelength laser and the more wavelength It is effective to irradiate a combination of long lasers, that is, to irradiate a laser having a wavelength of 370 nm or more and less than 400 nm and a laser having a wavelength of 400 nm or more and 450 nm or less at the same time or before and after. is there. In addition, when irradiating laser of these two wavelengths before and after, whichever may be first.

  In order to increase the curing rate, there are other methods such as heating a plastic substrate, but in the manufacturing process of flexible display elements such as flexible displays and electronic paper, avoid thermal damage to the display medium and plastic substrate. Therefore, a process at a high temperature is not preferable.

  The photocurable resin used in the method for producing a flexible display element of the present invention is not particularly limited as long as it is polymerized and cured in a wavelength range of 370 nm to 450 nm, but in general, (meth) acrylate Compounds and epoxy compounds are suitable. As an example of such a photo-curing resin, for example, 3170B adhesive manufactured by ThreeBond Co., Ltd., which is a one-component, solvent-free visible-light curable resin mainly composed of acrylate can be given.

  Then, the manufacturing apparatus used for manufacture of the flexible display element of this invention is demonstrated. FIG. 3 is a schematic cross-sectional view showing a state in which a photocurable resin is interposed on the peripheral edge of a plastic substrate, and FIG. 4 is a schematic perspective view of a manufacturing apparatus used for manufacturing the flexible display element of the present invention. The manufacturing apparatus shown in FIG. 4 emits a mounting table 8 on which a plastic substrate with a photo-curing resin interposed therebetween, and a laser 13 having a wavelength of 370 nm or more and 390 nm or less provided above the mounting table 8. And an XY moving mechanism 12 that moves the laser head 9 in parallel with the mounting table 8 so as to irradiate the photo-curable resin. The XY moving mechanism 12 is configured to hold the laser head 9 on the mounting table 8 and to move in parallel in the X-axis direction and the Y-axis direction.

  As shown in FIG. 3, a photocurable resin is interposed between the plastic substrates 10, and a photocurable resin line, a so-called glue line 11, is formed on the peripheral portion of the plastic substrate. This is fixed on the mounting table 8 of the irradiation apparatus shown in FIG. 4 in a state where the positions are not shifted from each other, and the laser emitted from the laser head 9 is directed to the glue line 11 through the upper plastic substrate 10. Irradiate to trace this.

  In manufacturing a flexible display element having a structure in which a photocurable resin is interposed so as to cover the entire surface of a display medium formed on one plastic substrate, the XY moving mechanism 12 is a photocurable resin. The laser head 9 is sequentially scanned so that the laser is irradiated to the entire range where the mold resin is interposed.

  Next, the laser module will be described. FIG. 5 is a schematic perspective view showing one embodiment of a laser head and a laser module connected to the laser head. The laser head 9 is connected to a laser module 15 by an optical fiber 14. In the laser module 15, a GaN laser diode having a central wavelength of 405 nm is mounted in a can package 17, and the emitted light is coupled by a lens 16 to a multimode optical fiber 14 having a quartz core having a diameter of 60 microns. ing. The optical fiber 14 is introduced into the laser head 9 and collimated by a collimator lens 18 into a parallel beam having a beam diameter of about 2 mm.

  FIG. 6 is a schematic perspective view showing another aspect of the laser head and the laser module connected to the laser head. The laser module shown in FIG. 6 is a two-wavelength laser module that can selectively emit two wavelengths, and the first laser module 19 includes a metal can package including a GaN-based laser diode that oscillates with a center wavelength of 405 nm. The second laser module 20 includes a metal can package including a GaN-based laser diode that oscillates with a central wavelength of 375 nm, and an optical system that couples light from the multimode fiber 21 with a core diameter of 33 microns. Is coupled to a multimode fiber 21 having a core diameter of 33 microns.

  The two multimode fibers 21 are introduced into the fiber multiplexer 22 and are combined into one multimode fiber 23 having a core diameter of 60 microns. In the figure, A, B and C respectively represent the cross section of the multimode fiber 21 before multiplexing, the end face of the multimode fiber 21 tapered to a diameter of 70%, and the end face of the multimode fiber 23 having a core diameter of 60 microns. Show. The multi-mode fibers 21 having a core diameter of 33 microns are fused with each other at the sides by being drawn hot, and are reduced in diameter. By fusing the end face B to the end face C of the multi-mode fiber 23 having a core diameter of 60 microns, the two-wavelength laser from the multi-mode fiber 21 having two core diameters of 33 microns becomes a multi-mode fiber having a core diameter of 60 microns. 23 is introduced into the laser head 9. From the emitting end of the laser head 9, lasers of 405 nm and 375 nm are emitted as parallel beams having a diameter of about 4 mm, and these two-wavelength lasers can be emitted simultaneously or before and after.

  Hereinafter, the manufacturing method of the flexible display element of this invention is demonstrated in detail using an Example.

(Example 1)
A PEN substrate with a thickness of 100 microns is prepared by adding a 30-micron diameter bead spacer to a 3170B adhesive manufactured by ThreeBond, which is a one-component, solvent-free, visible-light curable resin based on acrylate. It applied to the peripheral part using the dispenser. The adhesive width after application was about 0.5 mm. Another PEN substrate was overlaid with the adhesive in between. At this time, the width of the adhesive expanded to about 2 mm. This is fixed on the mounting table 8 of the irradiation apparatus shown in FIG. 4 in a state where the positions are not shifted from each other, and the laser emitting portion of the laser head 9 is held at a height of about 10 mm from the upper substrate, while being 6 mm. The light with a central wavelength of 405 nm emitted from the laser head 9 was irradiated at a speed of / s so as to trace the glue line 11 through the upper PEN 10 substrate. At this time, the spot diameter of the laser 13 on the substrate was about 2 mm, the laser output from the laser head 9 was about 400 mW, and the irradiation energy density of the laser on the upper substrate was about 3 J / cm ² . The pair of sealed PEN substrates showed a peel strength of 7 N / mm or more.

(Example 2)
A three-component, solvent-free, visible-light-curable resin made by ThreeBond Co., Ltd. on a PEN substrate having a thickness of 100 microns on which a spacer having a height of 30 microns is formed by a display medium and a photoresist. A PEN substrate having a thickness of 100 microns coated with 3170B adhesive was overlaid with the adhesive facing the display medium. In a state where they are fixed so as not to be displaced from each other, they are placed on the mounting table 8 of the manufacturing apparatus shown in FIG. 4 to which the two-wavelength laser module shown in FIG. 6 is connected. The entire surface of the adhesive was irradiated through the upper PEN substrate 10 while sequentially scanning the laser head using the -Y moving mechanism. At this time, the output of the first laser module 19 (405 nm) is set to 400 mW and the output of the second laser module (375 nm) is set to 200 mW while holding the emitting portion of the laser head 9 at a height of about 10 mm from the upper substrate. Irradiated simultaneously and scanned at 4.5 mm / s. The spot diameter of the laser on the substrate was about 4 mm, and the irradiation energy density of the laser on the upper PEN substrate was about 3.3 J / cm ² for the two wavelengths. The pair of sealed PEN substrates showed a peel strength of 7 N / mm or more.

  As described above, in the method for manufacturing a flexible display element of the present invention, a laser having a wavelength of 370 nm or more and 450 nm or less is irradiated to the photocurable resin portion, so that deterioration of both the plastic substrate and the display medium is minimized. However, it is possible to maximize the energy utilization efficiency of the laser.

Graph showing absorption spectrum and effective wavelength curve of PEN and photocurable resin Partial schematic sectional view of a flexible display element sandwiched between plastic substrates Schematic sectional view showing a state in which a photo-curing resin is interposed on the peripheral edge of a plastic substrate The schematic perspective view of the manufacturing apparatus used for manufacture of the flexible display element of this invention. Schematic perspective view showing one aspect of a laser head and a laser module connected thereto Schematic perspective view showing another embodiment of a laser head and a laser module connected to the laser head

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Absorption spectrum of PEN 2 Absorption spectrum of photocurable resin 3 Effective wavelength curve 8 Mounting base 9 Laser head 10 Plastic substrate 11 Glue line 12 XY movement mechanism 13 Laser 14 Optical fiber 15 Laser module 18 Collimator lens 22 (22 ' ) Plastic substrate 23 (23 ') Barrier layer 24 Display medium 25 Passivation film 26 Photocurable resin layer

Claims (5)

In the method of manufacturing a flexible display element in which the plastic substrates are bonded to each other by interposing a photocurable resin for sealing a display medium such as a liquid crystal between the plastic substrates,
A method for manufacturing a flexible display element, wherein the plastic substrate is bonded to each other by irradiating the photocurable resin portion with a laser having a wavelength of 370 nm to 450 nm through at least one of the plastic substrates. In the method of manufacturing a flexible display element in which the plastic substrates are bonded to each other by interposing a photocurable resin for sealing a display medium such as a liquid crystal between the plastic substrates,
Irradiating the light-curing resin portion with a laser having a wavelength of not less than 370 nm and less than 400 nm and a laser having a wavelength of not less than 400 nm and not more than 450 nm at the same time or before and after through at least one plastic substrate. A method for manufacturing a flexible display element, comprising bonding the plastic substrates together.   3. The method of manufacturing a flexible display element according to claim 1, wherein the plastic substrate is polyethylene naphthalate.   A mounting table on which two plastic substrates with a photo-curable resin interposed between them for sealing a display medium such as a liquid crystal are interposed, and a wavelength of 370 nm to 450 nm provided above the mounting table A flexible display element comprising: a laser head that emits the laser; and a moving mechanism that moves the laser head in parallel with the mounting table so that the laser irradiates the photocurable resin. Manufacturing equipment.   5. The laser head is a laser having a wavelength of 370 nm or more and less than 400 nm and a laser having a wavelength of 400 nm or more and 450 nm or less, and selectively emits a laser having a wavelength difference of 20 nm or more. Manufacturing apparatus for flexible display elements.

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