JP2014089227A - Microlens array manufacturing method and microlens array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microlens array manufacturing method which enables manufacturing of microlenses having high refractivity, high transmittance, and superior durability at low manufacturing cost.SOLUTION: A microlens array manufacturing method includes; a step S101 for preparing a first dispersion liquid by dispersing glass frits in a first dispersion medium; a step S102 for preparing a second dispersion liquid by dispersing microparticles made of a metallic oxide having a higher melting point and a higher refractive index than the glass frits in a second dispersion medium; a step S103 for preparing a paste of a lens base material by mixing the first dispersion liquid and the second dispersion liquid; a step S105 for filling a plurality of recesses formed on one surface of a substrate with the paste of the lens base material; and a step S106 for vitrifying the glass frits by heating and baking the lens base material filling the recesses at a temperature lower than the melting point of the metallic oxide.

Description

The present invention relates to a microlens array manufacturing method and a microlens array.

As a display device that projects an image on a screen, a projection display device is known. In such a projection display device, a liquid crystal panel (liquid crystal light shutter) is mainly used for image formation. In this liquid crystal panel, for example, a liquid crystal driving substrate (TFT substrate) having a thin film transistor (TFT) for controlling each pixel and a pixel electrode, and a counter substrate for a liquid crystal panel having a black matrix, a common electrode, etc. It becomes the structure joined via. In the liquid crystal panel having such a configuration (TFT liquid crystal panel), since the black matrix is formed in a portion other than the portion of the counter substrate for the liquid crystal panel, the region of light transmitted through the liquid crystal panel is limited. For this reason, the light transmittance decreases.

In order to increase the light transmittance, a counter substrate for a liquid crystal panel is known in which a large number of microlenses are provided at positions corresponding to each pixel. Thereby, the light which permeate | transmits the opposing board | substrate for liquid crystal panels is condensed by the opening formed in the black matrix, and the transmittance | permeability of light increases. As a method for forming such a microlens, for example, an uncured photocurable resin is supplied to a substrate with recesses having a plurality of recesses for forming microlenses, and a smooth transparent substrate (cover glass) is joined. A so-called 2P method is known in which a resin is cured by pressing and intimate contact (see, for example, Patent Document 1).

However, in the method according to Patent Document 1, since a resin material is used for forming the microlens substrate, it is difficult to obtain a microlens substrate having sufficient durability. In particular, since the photocurable resin used in the 2P method is likely to cause deterioration of the resin material due to light having a short wavelength, sufficient light resistance may not be obtained. In addition, since the microlens substrate is formed using the three members of the resin layer composed of the photocurable resin, the cover glass, and the substrate with the recesses, distortion or the like is likely to occur due to a difference in thermal expansion coefficient. As a result, characteristics such as optical characteristics may be degraded. For example, a process such as alignment of the cover glass is necessary, and the manufacturing process is complicated. In addition, when the cover glass is polished to obtain the optimum optical path length, dirt due to polishing occurs, and therefore an excessive cleaning step is required. By performing such cleaning, the resin layer is configured. There was a possibility that the resin material to be deteriorated. As a result, the quality may be reduced, and the yield may be reduced.

In addition, a manufacturing method of a microlens array using a glass material excellent in optical characteristics and durability of a microlens as a microlens material is also known (see, for example, Patent Document 2).

In the method according to Patent Document 2, the lens base material is heated at a temperature higher than its glass transition point (Tg) and pressed against the substrate recess where the microlens is formed by pressure. In order to reliably fill the lens substrate, it must be heated to a temperature greatly exceeding Tg. However, since there is a risk of damage due to pressure contact, the lens base material is required to have a Tg lower than that of the substrate and to reduce the difference in linear expansion coefficient from a predetermined value. However, in order to satisfy these requirements, although the lens material is required to have a higher refractive index, only a minimum refractive index for fulfilling the lens function can be realized.

Therefore, a method for manufacturing a glass microlens having excellent durability and a high refractive index has been proposed (see, for example, Patent Document 3). In the manufacturing method of Patent Document 3, a lens base material filling step of filling a concave portion of a substrate with concave portions with a paste-like lens base material kneaded with a lens material powder as a main material, and a filled lens base material, And a firing step for vitrification.

JP 2001-92365 A JP 2006-313279 A JP 2011-59156 A

Although it is not clearly described in the method of Patent Document 3, the lens material powder, that is, the glass main material, is obtained by once calcination of the raw material and vitrification, and then using the powdered material. Guessed. However, the glass main material used in the method of Patent Document 3 contains a metal oxide in order to increase the refractive index. Therefore, in the process for producing the glass main material, it is necessary to calcinate the metal oxide together with silicon oxide and boron oxide, and then pulverize it.

However, generally, metal oxides have a higher melting point than ordinary glass materials such as silicon oxide, and therefore glass materials containing metal oxides also have a higher glass transition point. Therefore, in the method of Patent Document 3, the firing temperature in the vitrification step when producing the glass main material is significantly higher than the firing temperature in the normal vitrification step, which increases the production cost. .

The present invention has been made in view of the above circumstances, and the object of the present invention is to provide a microlens having excellent optical characteristics, in particular, high refraction and high translucency, and excellent durability. It is an object of the present invention to provide a microlens array manufacturing method that can be obtained at a low manufacturing cost and a microlens array obtained by this manufacturing method.

The method for producing a microlens array of the present invention includes a step of preparing a first dispersion by dispersing glass frit in a first dispersion medium, and a metal oxide having a higher melting point and higher refractive index than the glass frit. Preparing a second dispersion by dispersing the fine particles in a second dispersion medium, and mixing the first dispersion and the second dispersion to prepare a paste-like lens substrate. A step of filling the plurality of recesses formed on one surface side of the substrate with the paste-like lens base material, and the lens base material filling the plurality of recesses from the melting point of the metal oxide. Heating and baking at a low temperature to vitrify the glass frit.

According to this method of manufacturing a microlens array, a glass substrate is prepared by heating and firing a lens substrate prepared by mixing the first dispersion and the second dispersion at a temperature lower than the melting point of the metal oxide. Therefore, the microlens formed in the recess is made of an inorganic material in which fine metal oxide particles are dispersed in glass made of glass frit. Therefore, it is excellent in durability and having high refractive properties by dispersing fine particles of a metal oxide having a high refractive index, and also has high translucency. In addition, since the metal oxide fine particles are dispersed in the second dispersion medium to prepare the second dispersion liquid, aggregation of the metal oxide fine particles can be prevented and a good dispersion state can be maintained. Then, since the paste-like lens base material is prepared by mixing the second dispersion liquid maintaining such a good dispersion state with the first dispersion liquid, the metal oxide fine particles in the lens base material As for, a good dispersion state can be maintained as it is. Therefore, the microlens obtained after firing has good lens characteristics because the metal oxide fine particles are uniformly dispersed. In the step of firing the lens substrate, the metal oxide is not vitrified, and thus heated at a temperature lower than the melting point of the metal oxide. For example, a conventional glass material containing a metal oxide is high. A step of calcination at a temperature and vitrification becomes unnecessary, which can reduce the manufacturing cost.

In the method of manufacturing the microlens array, the metal oxide fine particles are preferably nanoparticles having a particle size of 10 nm to 100 nm. Thus, by using nanoparticles of a metal oxide having a low transmittance (translucency) compared to glass, the transmittance (translucency) of the obtained microlens is sufficiently increased and the lens characteristics are improved. be able to.

In the method of manufacturing the microlens array, the metal oxide is preferably one or more selected from titanium oxide, zirconium oxide, and zinc oxide. Thus, by using a material having a higher refractive index as the metal oxide, the refractive index of the obtained microlens can be sufficiently increased, and the lens characteristics can be improved.

In the method of manufacturing the microlens array, in the step of preparing the paste-like lens base material, the compounding ratio of the metal oxide fine particles represented by the following formula in the lens base material is 5% by weight or more. It is preferable to make it 30% by weight or less. Compounding ratio = [weight of metal oxide fine particles / (weight of glass frit + weight of metal oxide fine particles) × 100] Metal oxide has lower transmittance (translucency) than glass. By setting the ratio to 30% by weight or less, the transmittance (translucency) of the obtained microlens can be suppressed to a desired good transmittance, while a desired high refractive index (high refractive index) is obtained. Therefore, it is preferable that the blending ratio is 5% by weight or more.

In the method of manufacturing the microlens array, in the step of preparing the first dispersion, a binder resin is dissolved or dispersed in the first dispersion medium, and then the glass frit is dispersed. In the step of preparing a dispersion liquid and mixing the first dispersion liquid and the second dispersion liquid to prepare a paste-like lens substrate, in the first dispersion liquid during the mixing process, It is preferable to carry out by dropping the second dispersion. In this way, by dissolving or dispersing the binder resin in the first dispersion, it is possible to impart a desired viscosity to the paste-like lens base material, and filling the lens base material into the substrate recess. Becomes easier. Further, in the step of preparing the lens substrate, the second dispersion is dropped into the first dispersion during the mixing process, so that the dispersion state of the metal oxide fine particles in the second dispersion is changed. By mixing this with the first dispersion while maintaining good, the metal oxide fine particles can be well dispersed in the obtained lens base material. Further, a good dispersion state of the metal oxide fine particles can be realized by a short mixing process, and the viscosity of the obtained lens substrate can be more uniformly prepared.

The microlens array of the present invention is manufactured by the above manufacturing method. According to this microlens array, it has high translucency and high refraction, and has excellent durability. Therefore, it is suitable for a liquid crystal panel used in a liquid crystal light valve of a projection display device that is placed in a high temperature environment for a long time. In addition, since the manufacturing cost can be reduced, it contributes to the cost reduction of the liquid crystal panel, for example.

(A), (b) is a figure which shows the microlens array of 1st Embodiment. It is a flowchart which shows the manufacturing process of 1st Embodiment. (A)-(e) is a sectional side view which shows the manufacturing process of the board | substrate which has a recessed part. (A)-(d) is a figure which shows a lens base material filling process. It is a flowchart which shows the manufacturing process of 2nd Embodiment. (A)-(d) is a figure which shows a lens base material filling process. It is a schematic diagram of the optical system of the projection type display apparatus using this invention. It is a schematic sectional side view of the liquid crystal panel using this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

First Embodiment FIGS. 1A and 1B are diagrams showing a schematic configuration of a first embodiment of a microlens array according to the present invention. FIG. 1A is a plan view, and FIG. It is AA arrow sectional drawing of a). 1A and 1B, reference numeral 10 denotes a microlens array. The microlens array 10 has a lens material fixed to a substrate 12 on which a plurality of recesses 12a corresponding to a plurality of microlenses 11 are formed. Thus, the microlens 11 is formed.

As shown in FIG. 1B, the microlens 11 is obtained by dispersing metal oxide fine particles 11b having a high refractive index in a glass 11a. As a result, the microlens 11 has a higher refractive index than the glass substrate 12, and light incident from the external Q on the substrate 12 side is refracted when emitted to the outside on the microlens 11 side. It functions to collect light in the direction.

FIG. 2 shows a flowchart of the manufacturing method of the microlens 11 as the first embodiment of the manufacturing method according to the present invention. [First Dispersion Preparation Step] As a pre-step for adjusting the lens base material to be the microlens 11, first, a first dispersion is prepared (S101). As materials, fine particle glass frit, a binder mainly composed of a resin component for connecting the glass frit, and a first dispersion medium are used. In addition to these main materials, for example, a plasticizer may be added as necessary. And a 1st dispersion liquid is obtained by mixing these and adjusting to paste form.

The glass frit preferably has a low linear expansion coefficient of, for example, 30 × 10 ⁻⁷ / ° C. or less, and a borosilicate glass frit is suitably used in this embodiment. The borosilicate glass frit is, for example, powdered after firing a mixture of silicon oxide and boron oxide and vitrifying, and a commercially available product can be used. However, the glass frit is not limited to the borosilicate glass frit, and other glass frit such as soda glass, crystalline glass, and crown glass can also be used.

The particle size of the glass frit is preferably 10 μm or less in order to ensure fluidity. On the other hand, making the particle size finer is preferable in terms of product production, but from the production of glass fine particles, the cost increases significantly, such as equipment cost and a long production process, and the particle size It becomes more difficult to equalize. Accordingly, a particle diameter of 10 nm or more is preferable because of restrictions on the production of fine particles.

Although it will not specifically limit if it is a resin component as a binder, In addition to the performance which connects a glass frit, it needs to have the property of evaporating reliably in the below-mentioned baking process. As such a binder, for example, a cellulose-based resin, polyvinyl butyral (PVB), or the like is preferably used. In the present embodiment, a cellulose-based resin is used.

As the first dispersion medium, low boiling point type ethanol, acetone, medium boiling point type butanol, toluene, high boiling point type isophorone, terpineol and the like can be used. However, since it is necessary to prepare the lens base material in a paste form as will be described later, it is preferable to use a suitable paste material for the first dispersion medium. It is preferable to use a mixture of seeds. In this embodiment, terpineol suitable as a paste material is used as the first dispersion medium. By using this terpineol, it becomes possible to easily fill a lens substrate to be described later by screen printing (squeegee printing).

In order to prepare the first dispersion using such a material, first, a material obtained by adding a binder resin to the first dispersion medium is put in a ball mill apparatus and mixed for a sufficient time (for example, all day and night). . As a result, the binder resin is dissolved in the first dispersion medium. Subsequently, glass frit is put into this solution, followed by mixing with a three-roll mill apparatus, thereby preparing a first dispersion liquid in which the glass frit is dispersed. The first dispersion prepared as described above has a high viscosity due to the binder resin dissolved and the glass frit dispersed therein, and is in the form of a paste. In addition, about the process which disperse | distributes a glass frit, it can disperse | distribute a glass frit sufficiently uniformly by performing about several minutes to about several tens of minutes.

In addition, about each compounding quantity of a 1st dispersion medium, binder resin, and glass frit, a binder resin can be dissolved favorably with a 1st dispersion medium, and desired viscosity in the state which disperse | distributed glass frit. That is, the viscosity is set so as to be suitable for screen printing described later.

[Second Dispersion Preparation Step] As a pre-step for adjusting the lens substrate to be the microlens 11, a second dispersion is prepared separately from the step of preparing the first dispersion (S102). As materials, metal oxide fine particles and a second dispersion medium are used. Then, the second dispersion is obtained by mixing these and dispersing the fine particles of the metal oxide well.

As the metal oxide, titanium oxide, zirconium oxide (zirconia) and zinc oxide, which are high refractive index materials, are preferable, and therefore one or more selected from these are used. The refractive index (n) and melting point (mp) of these metal oxides are shown below. Titanium oxide (TiO ₂ ): Refractive index 2.7, melting point 1870 ° C. Zirconium oxide (ZrO ₂ ): Refractive index 2.13, melting point 2715 ° C. Zinc oxide (ZnO): Refractive index 2.0, melting point 1975 ° C. As for titanium oxide (TiO ₂ ), the refractive index and melting point of the anatase type (tetragonal crystal) having the highest refractive index are shown. In this embodiment, titanium oxide (anatase type) having the highest refractive index is used as the metal oxide.

As such metal oxide fine particles, nanoparticles having a particle size of 10 nm to 100 nm are preferably used, and nanoparticles having a particle size of 10 nm to 30 nm are more preferably used. Since metal oxide has lower transmittance (translucency) than glass, if the particle size of the fine particles exceeds 100 nm, the transmittance (translucency) decreases, and as a microlens for a liquid crystal panel, It is not preferable. If nanoparticles of 30 nm or less are used, the transmittance (translucency) is hardly lowered with respect to glass, and therefore, it is more suitable as a microlens for a liquid crystal panel. On the other hand, when the thickness is less than 10 nm, the production becomes difficult and the van der Waals force makes it easier to aggregate in the dispersion liquid (dispersion medium), and the fine particles are uniformly dispersed in the obtained microlens. It will be difficult. In addition, about such a nanoparticle with a particle size of 10 nm or more and 100 nm or less, for example, a gas evaporation method. It can be produced by an atomizing method, a chemical reduction method or the like.

As the second dispersion medium, the same dispersion medium as that described above can be used. In particular, a metal oxide (titanium oxide) can be favorably dispersed without agglomeration, and the binder resin can be dissolved and is highly compatible with the first dispersion medium. . For example, an ethanol-based solvent (dispersion medium) is preferably used. In this embodiment, ethanol is used as the second dispersion medium.

In order to prepare the second dispersion using such a material, a mixture obtained by adding metal oxide fine particles to the second dispersion medium is put in a three-roll mill apparatus and mixed for several minutes to several tens of minutes. . As a result, a second dispersion liquid in which the metal oxide fine particles are sufficiently uniformly dispersed in the second dispersion medium can be prepared. In addition, about each compounding quantity of the 2nd dispersion medium and metal oxide microparticles | fine-particles, the desired viscosity in the state which disperse | distributed metal oxide microparticles | fine-particles to the 2nd dispersion medium, ie, the viscosity suitable for screen printing mentioned later Set to be.

[Lens Substrate Preparation Step] Next, the first dispersion and the second dispersion obtained in the above step are mixed to prepare a paste-like lens substrate (S103). In this preparation step, the first dispersion prepared in the first dispersion preparation step is again put into a three-roll mill device and mixed (kneading), or the first dispersion is prepared. Thereafter, while continuing the mixing process (kneading process) with a three-roll mill apparatus, the second dispersion liquid is dropped into the first dispersion liquid during the mixing process. Although there is no particular limitation on the dropping speed, for example, a sufficient time is taken while visually confirming that the second dispersion is well dispersed with respect to the first dispersion. Is preferred.

As described above, by dropping the second dispersion liquid into the first dispersion liquid during the mixing process, the dispersion state of the metal oxide fine particles in the first dispersion liquid is maintained satisfactorily. By mixing with the dispersion liquid 2, the metal oxide fine particles can be favorably dispersed in the obtained lens substrate. Further, a good dispersion state of the metal oxide fine particles can be realized by a short mixing process. Furthermore, the viscosity of the obtained paste-like lens substrate can be more uniformly prepared.

Here, with respect to the mixing ratio of the first dispersion and the second dispersion, the mixing ratio of the metal oxide fine particles to the solid content in the obtained lens base material, that is, the total of the glass frit and the metal oxide fine particles. It is preferable that the weight of the metal oxide fine particles in the weight is 5% by weight or more and 30% by weight or less. In addition, since the binder resin in the first dispersion liquid evaporates in the baking step described later, it does not become a solid content in the obtained lens base material. The compounding ratio (% by weight) of the metal oxide fine particles is shown in the following formula. Compounding ratio = [weight of metal oxide fine particles / (weight of glass frit + weight of metal oxide fine particles)] × 100

As described above, a metal oxide such as titanium oxide has a lower transmittance (translucency) than glass. Therefore, by setting the blending ratio to 30% by weight or less, the transmittance (translucency) of the obtained microlens can be suppressed to a desired good transmittance. On the other hand, in order to obtain a desired high refractive index (high refractive property), it is preferable that the blending ratio is 5% by weight or more.

[Substrate manufacturing step] Separately from the steps up to the lens base material preparation step (S103), the substrate 12 having the recess 12a is formed (S104). 3A to 3E show an example of a method for manufacturing a substrate having a recess 12a.

<Film Formation Process for Mask Formation> As shown in FIG. 3A, first, a glass substrate 20 having a uniform thickness and no scratches is prepared, and the surface of the glass substrate 20 is used for mask formation. A film 21 is formed. The mask forming film 21 functions as a mask by forming an opening (initial hole) in a later step. As will be described later, the mask forming film 21 is formed with an initial hole 22 by laser irradiation, and then a recess is formed in the glass substrate 20 from the initial hole 22 by etching. Therefore, the mask forming film 21 preferably has resistance to etching. That is, the etching rate of the mask forming film 21 is preferably sufficiently smaller than that of the glass substrate 20.

Therefore, the material of the mask forming film 21 is, for example, a metal such as Cr, Au, Ni, Pt, or an alloy containing two or more selected from these, an oxide such as Cr, Au, Ni, Pt, etc. (Metal oxide), silicon, resin and the like are used. Moreover, it is good also as a several laminated structure which consists of a different material like Cu and Au or oxide Cr and Cr. The method for forming the mask forming film 21 is not particularly limited, and an optimum method for the film material is appropriately selected and used from an evaporation method, a sputtering method, a CVD method, and the like. The film thickness is appropriately set according to the initial hole formation conditions and etching conditions, but is preferably about 0.01 μm to 0.2 μm.

<Initial Hole Formation Step> After forming the mask forming film 21 on the surface of the glass substrate 20, as shown in FIG. 3B, the mask forming film 21 has an initial hole that becomes a mask opening in the later-described etching. 22 is formed at a position corresponding to the microlens formation position. Thereby, the mask 23 having a predetermined opening pattern is obtained.

As a method for forming the initial hole 22, laser light irradiation, etching treatment, or the like is employed. In particular, high positional accuracy can be maintained, and the interval between the adjacent initial holes 22 can be accurately controlled. Therefore, laser beam irradiation is preferably employed.

<Etching Step> Next, as shown in FIG. 3C, a recess 24 is formed in the glass substrate 20 by etching through the initial hole 22 formed in the mask 23. In the present embodiment, the recess 24 is formed by wet etching. Although the etching solution is not particularly limited, in this embodiment, since the glass substrate 20 is used as the substrate, a hydrofluoric acid-based etching solution containing hydrofluoric acid (hydrogen fluoride) is used. By using a hydrofluoric acid-based etchant, the glass substrate 20 can be etched more selectively, and the recesses 24 can be suitably formed.

By etching the glass substrate 20 covered with the mask 23 in which the initial holes 22 are formed, the glass substrate 20 has the initial holes 22 formed in the mask 23 as shown in FIG. A recess 24 is formed by etching with an etching solution from a portion where no material is present. By gradually etching the glass substrate 20 by controlling the etching time and the like, a recess 24 having a predetermined depth can be formed as shown in FIG.

<Mask Removal Step> Thereafter, by removing the mask 23 by etching or the like, a substrate 25 having a large number of recesses 24 can be obtained as shown in FIG.

[Lens Substrate Filling Step] Next, in the concave portion 24 of the substrate 25 obtained in this substrate manufacturing step (S104), as shown in FIGS. The paste-like lens substrate obtained in (1) is filled (S105). 4A is a plan view schematically showing the substrate 25 viewed from the side where the recess 24 is formed, and FIG. 4B is a cross-sectional view taken along the line B-B in FIG. 4 (c) and 4 (d) are explanatory views of the lens base material filling process.

First, pretreatment such as cleaning and drying is performed on the substrate 25 having the recess 24 shown in FIGS. 4A and 4B manufactured in the substrate manufacturing step (S104) as necessary. Next, the paste-like lens base material is filled in the recess 24 of the substrate 25 by a screen printing method. First, as shown in FIG. 4C, a metal screen printing plate (metal mask) 30 is arranged on the substrate 25 so as to be aligned with the lens forming region.

A mesh pattern 30 a is formed on the screen printing plate 30 according to the filling amount of the lens base material 31 at a position corresponding to the recess 24. This mesh pattern is determined by the fluidity (viscosity) of the paste-like lens base material 31 and the depth size of the recess 24 of the substrate 25. The simplest pattern is the entire lens formation range. It is also possible to form a so-called solid pattern that is imprinted on the substrate. The thickness of such a screen printing plate 30 is set depending on the solid content concentration of the lens substrate 31, but in order to ensure durability against mask cleaning or the like, the thickness is, for example, 25 μm or more, preferably about 50 μm. Use one.

After the screen printing plate 30 is thus arranged, the lens base material 31 is arranged on the screen printing plate 30, and then the lens base material 31 is leveled by the squeegee 32. Thereby, the paste-like lens base material 31 can be pressed and filled in the recess 24 of the substrate 25. By filling the lens base material 31 in the recess 24 in this way, as shown in FIG. 4D, a microlens array 33 before firing formed by filling the lens base material 31 is obtained.

[Baking Step] Next, the microlens array 33 before baking shown in FIG. 4D is heated and baked (S106). That is, in this firing step, the lens base material 31 filled in the recess 24 is heated and fired to form the microlens 11 shown in FIGS. 1 (a) and 1 (b). At this time, in the present invention, the heat is fired at a temperature higher than the softening point of the glass frit in the lens substrate 31 and lower than the melting point of the metal oxide (TiO ₂ ). For example, since the softening point temperature of borosilicate glass frit is 780 ° C. and the melting point of TiO ₂ (metal oxide) is 1870 ° C. as described above, the temperature is higher than 780 ° C. and lower than 1870 ° C., for example, Heating and firing is performed at a temperature about 50 to 100 ° C. higher than the softening point temperature of the glass frit.

Specifically, first, the pre-firing microlens array 33 is dried for about 30 minutes using an atmosphere drying furnace at 100 ° C. to 200 ° C. Next, the dried pre-fired microlens array 33 is fired in a firing furnace such as an electric furnace (S106). As a firing sequence, the heating temperature is increased at a temperature increase rate of 10 ° C./min up to the temperature at which the binder resin evaporates, that is, the binder removal temperature. In this embodiment, the binder removal temperature is about 450 ° C. to 500 ° C. Then, the binder removal temperature is maintained for a predetermined time to surely evaporate the binder resin.

After performing the binder removal treatment in this way, the heating temperature is increased at a temperature increase rate of 10 ° C./min up to a temperature higher than the softening point of the glass frit, in this embodiment, 850 ° C. Then, the heating temperature (firing temperature) is maintained for about 15 minutes to 60 minutes, and the glass frit is softened to be vitrified. Thereafter, the microlens array is returned to room temperature by natural cooling. Thereby, the microlens array 10 which has the microlens 11 in the recessed part 12a shown to FIG. 1 (a), (b) is obtained. Although the firing furnace is not limited to an electric furnace, it is necessary to perform firing in an apparatus that does not generate impurities such as active gas and soot in order to eliminate the influence on the lens substrate 31.

In many cases, the microlens array 10 obtained in this way is not a sufficiently flat surface because the surface on the microlens 11 side is a surface that is smoothed by the squeegee 32. Therefore, it is preferable to carry out processes such as “planar polishing” and “outer shape dicing (cutting)” after the firing process, if necessary.

As the planar polishing, the polishing is performed when the outer surface of the microlens does not have the desired specularity and flatness, or when a defect such as a scratch is found. Further, since the outer shape dicing is manufactured in the form of a wafer up to the firing step (S106) in a manufacturing line for manufacturing a plurality of microlens arrays 10 using a wafer, the step of dividing into individual microlens arrays 10 Is required. This is called outer shape dicing. In addition, when a portion other than the microlens formation range of the microlens array 10 is unnecessary, the unnecessary portion is generally deleted by dicing.

In the manufacturing method of the microlens array 10 of the present embodiment, the lens substrate 31 prepared by mixing the first dispersion and the second dispersion is heated at a temperature lower than the melting point of the metal oxide. Since the glass frit is vitrified by firing, the microlens 11 formed in the recess 24 is made of an inorganic material in which the metal oxide fine particles 11b are dispersed in the glass 11a made of glass frit. . Accordingly, the metal oxide fine particles 11b having excellent durability and high refractive index are dispersed, so that it has high refractive properties and also has high translucency.

Further, since the metal oxide fine particles 11b are dispersed in the second dispersion medium to prepare the second dispersion, the metal oxide fine particles 11b can be prevented from agglomerating to maintain a good dispersion state. And since the paste-like lens base material 31 is prepared by mixing the second dispersion liquid maintaining such a good dispersion state with the first dispersion liquid, the metal oxide in the lens base material 31 As for the fine particles 11b, a good dispersion state can be maintained as it is. Therefore, the microlens 11 obtained after firing has good lens characteristics because the metal oxide fine particles 11b are uniformly dispersed.

Further, in the step of firing the lens base material 31, the metal oxide is not vitrified, and therefore heated at a temperature lower than the melting point of the metal oxide, for example, 1000 ° C. or less. A step of baking the vitreous glass material at a high temperature to make it vitrified is unnecessary, and thus the manufacturing cost can be reduced.

The microlens array 10 of the present embodiment has high refraction and high translucency, and is excellent in durability. Therefore, it is suitable for a liquid crystal panel used in a liquid crystal light valve of a projection display device that is placed in a high temperature environment for a long time. In addition, since the manufacturing cost can be reduced, it contributes to the cost reduction of the liquid crystal panel, for example.

Second Embodiment FIG. 5 shows a flowchart of the second embodiment. The first dispersion liquid preparation step (S201), the second dispersion liquid preparation step (S202), the lens base material preparation step (S203), and the substrate manufacturing step (S205) in the present embodiment are the first in the first embodiment. Since this is the same as the dispersion liquid preparation step (S101), the second dispersion liquid preparation step (S102), the lens base material preparation step (S103), and the substrate manufacturing step (S104), description thereof will be omitted below. This embodiment is different from the first embodiment in that it includes a lens base sheet manufacturing step (S204) shown in FIGS.

[Lens Substrate Sheet Manufacturing Process] As shown in FIG. 6A, at least one surface of the paste-like lens base material adjusted and manufactured in the lens base material preparation step (S203) is a smooth surface. A paste-like lens substrate 51 is applied to a uniform thickness on the smooth surface of a film 50. In the present embodiment, a film using the film 50, using a PET material as a base material, and having SiO ₂ having a peeling action formed on the surface can be suitably used. Moreover, it is a board | substrate which has a smooth mirror surface at least 1 surface, Comprising: If the surface gave the peeling process, it can be used conveniently. For example, a metal plate such as a stainless steel plate, a copper plate, an aluminum plate, a resin substrate, a glass substrate, etc., in which a fluoride film having a peeling action on the substrate surface is formed by CVD or the like, can be used.

After the lens substrate 51 is applied, it is naturally dried or placed in a thermostatic bath to remove the solvent (solvent) component to obtain a sheet-like solid. Thereby, a so-called green sheet is formed. The green sheet has a certain level of strength as a solid substance, is not easily deformed or dents during handling, and has a high handling property during the manufacturing process. In addition, preparation and storage (storage) are possible in advance, and preparation of the lens substrate 51 is not required each time, so that it is an excellent manufacturing method suitable for mass productivity.

[Lens Substrate Filling Step] As shown in FIG. 6B, the lens base 51 (green sheet) manufactured in the above-described lens base sheet manufacturing step (S204) is similarly prepared in advance by a substrate manufacturing step (S205). It arrange | positions at the recessed part 24 side of the recessed part formation board | substrate 25 manufactured by (4). At this time, you may arrange | position with either the state stuck to the film 50, or the state which peeled the film 50.

Next, as shown in FIG. 6C, the lens base 51 is pressed in the direction of the arrow by the pressing device 52, and the lens base 51 is filled in the recess 24 of the substrate 25 (S206). At this time, it is preferable that heat is applied to the lens substrate 51 to increase the fluidity of the lens substrate 51 so that the lens substrate 51 is reliably filled with the recess 24. By this step, the pre-firing microlens array 33 is completed as shown in FIG.

[Baking Step] Thereafter, the microlens array 10 shown in FIGS. 1A and 1B is obtained by performing the baking step (S207) in the same manner as in the first embodiment.

Even in the manufacturing method of the microlens array of the present embodiment, as in the first embodiment, a microlens having high refraction and high translucency and having excellent durability can be manufactured at a relatively low manufacturing cost. Can be manufactured. The microlens array of the present embodiment is also suitable for a liquid crystal panel used for a liquid crystal light valve of a projection display device, and further contributes to cost reduction of the liquid crystal panel.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

[Usage Example] The microlens array obtained by the above embodiment is suitably used as a counter substrate of a liquid crystal panel used as a liquid crystal light valve in a projection display device. FIG. 7 shows a conceptual diagram of a projection display device. The projection display device 60 of this example is generally called a “liquid crystal projector”, and white light (white light flux) emitted from the light source 61 passes through the integrator lenses 62 and 63, and the light intensity (luminance distribution) of the white light. ) Is made uniform.

The white light that has passed through the integrator lenses 62 and 63 is reflected by the mirror 64, and further, blue light (B) and green light (G) are reflected by the dichroic mirror 65, and go to the dichroic mirror 69. The red light (R) passes through the dichroic mirror 65, is reflected by the mirror 66, is collected by the condenser lens 67, and travels toward the red liquid crystal light valve 68.

Of the blue light (B) and green light (G) directed to the dichroic mirror 69, the green light (G) is reflected by the dichroic mirror 69, and further condensed by the condenser lens 70 to be a liquid crystal light valve for green. 71 is incident. Further, the blue light (B) passes through the dichroic mirror 69, passes through the condenser lens 72, mirror 73, condenser lens 74, mirror 75, and condenser lens 76, and is collected, and the liquid crystal light valve 77 for blue is used. Is incident on.

The liquid crystal light valves 68, 71, and 77 are switching-controlled by drive circuits that operate based on the image signals of the respective colors to form images of the respective colors. The formed images of the respective colors enter the dichroic prism 78, are combined by the dichroic prism 78, and are projected onto the screen 80 through the projection lens 79.

As the liquid crystal light valves 68, 71, 77, a TFT liquid crystal panel 90 shown in FIG. 8 is used. The TFT liquid crystal panel 90 is composed of a TFT substrate (liquid crystal driving substrate) 91, a liquid crystal panel counter substrate 92 bonded to the TFT substrate 91, and liquid crystal sealed in a gap between the TFT substrate 91 and the liquid crystal panel counter substrate 92. And a liquid crystal layer 93.

The TFT substrate 91 is a substrate for driving the liquid crystal of the liquid crystal layer 93, and is provided in the vicinity of the glass substrate 91a, a number of pixel electrodes 91b provided on the glass substrate 91a, and the pixel electrode 91b. A plurality of thin film transistors (TFTs) 91c corresponding to 91b. In the TFT liquid crystal panel 90, the TFT substrate 91 and the liquid crystal panel counter substrate 92 are arranged so that the transparent electrode film (common electrode) 92 a of the liquid crystal panel counter substrate 92 and the pixel electrode 91 b of the TFT substrate 91 face each other. , They are joined at a certain distance.

The microlens array 92b of the present invention is applied to the counter substrate 92 for the liquid crystal panel. Incident light P incident from the microlens array 92b side is condensed when passing through the microlens 92c, passes through the liquid crystal layer 93 from the opening 92e of the black matrix 92d formed on the microlens array 92b, and passes through the liquid crystal layer 93. 91. At this time, the microlens array 92b has an effect of emitting the amount of incident light without being attenuated as much as possible, and it becomes difficult to maintain a predetermined focal length or focal position even with slight deformation. However, a stable quality can be maintained by applying the microlens array of the present invention while being a device that receives light from the light source 61 in FIG. It has become so.

DESCRIPTION OF SYMBOLS 10 ... Micro lens array, 11 ... Micro lens, 11a ... Glass, 11b ... Metal oxide fine particle, 12a ... Recessed part, 12 ... Substrate, 20 ... Glass substrate, 24 ... Recessed part, 25 ... Substrate, 30 ... Screen printing plate, 31 ... Lens substrate, 32 ... Squeegee, 33 ... Microlens array before firing

Claims (6)

A step of preparing a first dispersion by dispersing glass frit in a first dispersion medium, and dispersing metal oxide fine particles having a higher melting point and a higher refractive index than the glass frit in the second dispersion medium. Preparing a second dispersion, mixing the first dispersion and the second dispersion to prepare a paste-like lens base, and forming on one surface side of the substrate Filling the plurality of concave portions with the paste-like lens base material, and heating and baking the lens base material filled with the plurality of concave portions at a temperature lower than the melting point of the metal oxide. And a step of vitrifying the microlens array. 2. The method of manufacturing a microlens array according to claim 1, wherein the metal oxide fine particles are nanoparticles having a particle size of 10 nm to 100 nm. 3. The method of manufacturing a microlens array according to claim 1, wherein the metal oxide is one or more selected from titanium oxide, zirconium oxide, and zinc oxide. In the step of preparing the paste-like lens base material, the compounding ratio of the metal oxide fine particles represented by the following formula in the lens base material is 5 wt% or more and 30 wt% or less. The manufacturing method of the micro lens array as described in any one of Claims 1-3. Compounding ratio = [weight of metal oxide fine particles / (weight of glass frit + weight of metal oxide fine particles)] × 100 In the step of preparing the first dispersion, a binder resin is dissolved or dispersed in the first dispersion medium, and then the glass frit is dispersed to prepare the first dispersion. In the step of preparing the paste-like lens base material by mixing the dispersion liquid and the second dispersion liquid, the second dispersion liquid is dropped into the first dispersion liquid during the mixing process. The method for producing a microlens array according to claim 1, wherein the method is performed. The microlens array manufactured by the manufacturing method as described in any one of Claims 1-5.

Images