JP2014089228A - Microlens array manufacturing method and microlens array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microlens array manufacturing method which enables use of a substrate having superior mechanical and optical properties and provides more flexibility in selecting lens materials to be used by suppressing generation of cracks and warpage.SOLUTION: A method of manufacturing a microlens array 10 includes the steps of; filling lenticular recesses 12a of a microlens array substrate 12 with an inorganic lens material using a wet method; forming a lens layer 13 which fills at least the lenticular recesses 12a by baking the inorganic lens material; flattening the lens layer 13; and forming an optical path length adjustment film 14 on the flattened lens layer 13 using a vapor deposition method.

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 array substrate, it is difficult to obtain a microlens array substrate having sufficient durability.

On the other hand, 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 known (for example, see Patent Document 2). In this manufacturing method, a lens base material is heated at a temperature higher than its glass transition point (Tg), and is pressed against a substrate concave portion on which a microlens is formed by pressure, whereby a lens base material (lass material) is formed in the concave portion. To be filled.

JP 2001-92365 A JP 2006-313279 A

By the way, with improvement in characteristics of liquid crystal panels and the like, improvement of mechanical characteristics and optical characteristics of microlens array substrates is also required. In recent years, quartz glass substrates and neo-serum glass substrates, which have excellent characteristics such as high heat resistance and high transmittance, have been provided. Yes.

However, such a quartz glass substrate and a neo-ceram glass substrate have a low coefficient of thermal expansion (linear expansion coefficient: α) (for example, [α = 5.5 × 10 ⁻⁷ / ° C.] for quartz glass), and thus these substrates are used. When the lens base material (glass material) is filled in the concave portion by using and a microlens is formed, the lens base material that can be used is remarkably limited. That is, if the difference in thermal expansion coefficient between the substrate and the lens base material is large, cracks may occur in the microlens array due to the difference in thermal expansion coefficient when a thermal load is applied in the manufacturing process or usage pattern. Large warping may occur.

However, although the lens base material requires high refractive index and high transparency, these lenses satisfy these performances and have a low thermal expansion coefficient (close to the thermal expansion coefficient of quartz glass substrates and neoceram glass substrates). No material is currently provided. Therefore, as described above, cracks or large warpage may occur, and it is difficult to use a substrate having a low thermal expansion coefficient such as a quartz glass substrate or a neo-serum glass substrate as the microlens array substrate. Currently.

The present invention has been made in view of the above circumstances, and the object thereof is to enable the use of a substrate having excellent mechanical properties and optical properties and to suppress the occurrence of cracks and warpage. It is an object of the present invention to provide a method for manufacturing a microlens array in which the degree of freedom in selecting a lens material is increased, and a microlens array obtained by this manufacturing method.

The method for producing a microlens array of the present invention includes a step of filling the lens-shaped recess of the microlens array substrate having the lens-shaped recess with a wet method, and firing the inorganic lens material to at least Forming a lens layer filling the inside of the lens-shaped concave portion, flattening the lens layer, and forming an optical path length adjusting film on the lens layer after the flattening by a vapor deposition method. It is characterized by that.

According to this method of manufacturing a microlens array, the step of forming the lens layer in the lens-shaped recess and the step of forming the optical path length adjusting film on the lens layer are separated. The lens material and the optical path length adjusting film forming material can be separated. Here, when a microlens is formed by embedding a lens material in the concave portion of the substrate, the influence due to the difference in thermal expansion coefficient between the substrate and the microlens is particularly significant in the thickness direction of the substrate and the microlens. That is, the greater the thickness, the greater the influence, and the above-described cracks and warpage are likely to occur.

In the present invention, since the lens layer and the optical path length adjusting film are separately formed, the lens layer and the optical path length adjusting film are particularly thin in comparison with the case where the lens layer and the optical path length adjusting film are integrally formed. can do. In other words, since the thickness of the lens layer can be reduced, even if the difference in thermal expansion coefficient between this lens layer and the microlens array substrate increases, the effect of the difference in thermal expansion coefficient is equivalent to the reduction in the thickness of the lens layer. Can be reduced. On the other hand, the optical path length adjusting film needs almost no function as a lens, and it is only necessary to have a thickness as designed so that the focal point is at the optimum position. It may be the same level as. Accordingly, the degree of freedom in selecting the material is increased. Therefore, according to the present invention, it is possible to reduce the influence of the difference in thermal expansion coefficient between the lens layer and the microlens array substrate, thereby reducing the occurrence of cracks and warpage, in particular, by forming the lens layer thin. Therefore, even when a quartz glass substrate or a neo-ceram glass substrate having a small thermal expansion coefficient is used, the lens layer can be formed using a lens material having a relatively large thermal expansion coefficient as compared with these substrates. That is, a lens material having a high refractive index and a high transmittance can be appropriately selected and used, and therefore the degree of freedom in selecting a lens material to be used can be increased.

In addition, since the filling of the inorganic lens material is performed by a wet method with good embeddability, the lens layer can be formed in a relatively short time including the subsequent firing step, and thus the productivity can be improved. Furthermore, since the optical path length adjusting film is formed by a gas phase film forming method that easily reflects the shape of the base, the obtained optical path length adjusting film is a lens layer (including a microlens array substrate) that is a base after the planarization process. ) To reflect a flat surface. Therefore, the planarization process can be omitted for this optical path length adjusting film.

In the method of manufacturing the microlens array, in the step of filling the inorganic lens material by a wet method, the lens-shaped concave portion is filled by a wet method with a first inorganic lens material having a refractive index higher than that of the microlens array substrate. Subsequently, the first inorganic lens material is baked to form a first lens layer, and then a second inorganic lens material having a refractive index higher than that of the first inorganic lens material is placed in the lens-shaped recess. It is preferable to fill the first lens layer by a wet method. In this way, the thickness of the first lens layer and the thickness of the second lens layer obtained from the second inorganic lens material can be made thinner than the total thickness of the lens layer, respectively. , The influence due to the difference in thermal expansion coefficient between the first lens layer and the microlens array substrate and the influence due to the difference in thermal expansion coefficient between the second lens layer and the microlens array substrate can be reduced, respectively. Generation of cracks and warpage can be suppressed. Moreover, the lens characteristic of the lens layer obtained can be improved by combining the inorganic lens material from which a refractive index differs.

In the method for manufacturing a microlens array, it is preferable that a thermal expansion coefficient of the second lens layer formed by firing the second inorganic lens material is smaller than a thermal expansion coefficient of the first lens layer. In this way, since the first lens layer having a relatively large thermal expansion coefficient is sandwiched between the microlens array substrate having a relatively small thermal expansion coefficient and the second lens layer, when a thermal load is applied. Also, the first lens layer is pressed from both sides, so that the occurrence of cracks and warpage is suppressed.

In the method of manufacturing the microlens array, it is preferable that the thermal expansion coefficient of the optical path length adjusting film is smaller than the thermal expansion coefficient of the lens layer. In this way, since the lens layer having a relatively large thermal expansion coefficient is sandwiched between the microlens array substrate having a relatively small thermal expansion coefficient and the optical path length adjusting film, the lens can be used even when a thermal load is applied. Generation of cracks and warping is suppressed by pressing the layer from both sides.

In the step of flattening, it is preferable that the lens layer is flattened until at least a part of the microlens array substrate is exposed. In this way, it is possible to reduce the influence of the difference in thermal expansion coefficient between the lens layer and the microlens array substrate by reducing the thickness of the lens layer. In addition, the microlenses formed in the lens-shaped recess can be made independent of each other without being continuous with each other. Therefore, the transmission of stress can be prevented and the occurrence of cracks can be suppressed.

The microlens array of the present invention is manufactured by the above manufacturing method. According to this microlens array, it has high optical characteristics 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.

(A), (b) is a figure which shows the microlens array 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. (A)-(c) is explanatory drawing of the manufacturing process of a micro lens array. (A), (b) is a figure which shows the microlens array of 2nd Embodiment. (A)-(d) is explanatory drawing of the manufacturing process of a micro lens array. (A)-(c) is explanatory drawing of the manufacturing process of a micro lens array. 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 is a substrate (microlens) on which a plurality of concave portions (lens-shaped concave portions) 12a corresponding to a plurality of microlenses 11 are formed. As shown in FIG. 1B, a lens material is fixed to the (array substrate) 12 to form the microlens 11, a microlens layer 13 composed of the plurality of microlenses 11 is formed, and a microlens layer is further formed. The optical path length adjusting film 14 is formed on the substrate 13 and the substrate 12.

As the substrate 12, a quartz glass substrate or a neo-ceram glass substrate having high heat resistance and high transmittance is used in this embodiment. The microlens 11 is made of a glass material having a refractive index sufficiently higher than that of the substrate 12 and having a high transmittance (high translucency). The optical path length adjusting film 14 is formed of a material having a high transmittance (high translucency) such as SiO ₂ , and has a refractive index similar to that of the substrate 12, for example.

With such a configuration, the microlens array 10 refracts the light incident from the external Q on the substrate 12 side when it is emitted to the optical path length adjustment film 14 side by the microlens 11, and further focuses on the optical path length adjustment film 14. Is adjusted so as to be in the optimum position, so that the light is condensed at the designed position in the P direction.

Next, a first embodiment of a microlens array manufacturing method according to the present invention will be described. [Inorganic Lens Material Preparation Step] First, in order to form the microlens 11 by a wet method, a dispersion liquid of an inorganic lens material for forming the microlens 11 is prepared. As the material, for example, a particulate glass frit (inorganic lens material), a binder mainly composed of a resin component for connecting the glass frit, and a dispersion medium are used. In addition to these main materials, for example, a plasticizer may be added as necessary. And the dispersion liquid of inorganic lens material is obtained by mixing these and adjusting to paste form. In addition to the glass frit that is an inorganic lens material, this inorganic lens material dispersion contains a binder or dispersion medium that is an organic material. However, as will be described later, the binder and the dispersion medium are evaporated and disappeared during the firing process. Therefore, the dispersion liquid is finally only an inorganic component (inorganic lens material) made of glass frit.

The glass frit is not particularly limited, but the microlens 11 obtained therefrom has a refractive index higher than that of the substrate 12 by at least 0.1 or more, that is, a refractive index difference of 0.1 or more. The material to be used is used. Further, the thermal expansion coefficient is not greatly limited, and various types can be used. That is, although a substrate 12 having a relatively low thermal expansion coefficient such as a quartz glass substrate or a neo-ceram glass substrate is used, in this embodiment, unlike the conventional case, the heat between the substrate 12 and the microlens 11 to be formed is different. Since it is not necessary to make the difference in expansion coefficient excessively small and a certain degree of difference in thermal expansion coefficient can be allowed, for example, even a coefficient of thermal expansion α of about 30 × 10 ⁻⁷ / ° C. or higher can be used.

Examples of such glass frit include soda glass, crystalline glass, crown glass, potassium glass, lead glass, borosilicate glass, bismuth glass mainly composed of borosilicate glass and bismuth oxide, borosilicate glass and germanium oxide. Each glass frit such as germanium oxide-based glass containing as a main component can also be used. In the present embodiment, for example, a borosilicate glass frit having a thermal expansion coefficient α of about 30 × 10 ⁻⁷ / ° C. is preferably used. The borosilicate glass frit is obtained by baking a vitreous mixture of silicon oxide and boron oxide and then pulverizing it, and a commercially available one can 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 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 an inorganic lens material in a paste form as described later, it is preferable to use a suitable paste material for this dispersion medium. Therefore, a high boiling point type solvent or the like is used alone, or a plurality of types are mixed. And preferably used. In this embodiment, terpineol suitable as a paste material is used as a dispersion medium. By using this terpineol, it becomes possible to easily carry out filling of a dispersion liquid of an inorganic lens material described later by screen printing (squeegee printing).

In order to prepare a dispersion using such a material, first, a dispersion medium added with a binder resin is placed in a ball mill apparatus and mixed for a sufficient time (for example, all day and night). Thereby, binder resin is dissolved in a dispersion medium. Subsequently, glass frit is put into this solution and subsequently mixed by a three-roll mill apparatus to prepare a dispersion liquid in which the glass frit is dispersed, that is, a dispersion liquid of an inorganic lens material. The dispersion thus prepared has a high viscosity due to the binder resin dissolved therein and further 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.

About each compounding quantity of a dispersion medium, binder resin, and glass frit, binder resin can be dissolved favorably with a dispersion medium, and it is suitable for the desired viscosity, ie, the screen printing mentioned later in the state which disperse | distributed glass frit. Set so that the viscosity becomes high.

[Substrate Manufacturing Process] Separately from the above-described inorganic lens material preparation process, the substrate 12 having the recesses 12a is formed. An example of the manufacturing method of the board | substrate which has the recessed part 12a is shown to Fig.2 (a)-(e).

<Film Forming Process for Mask Formation> As shown in FIG. 2A, first, a glass substrate 20 made of a quartz glass substrate or a neo-serum glass substrate having a uniform thickness and no scratches and a cleaned surface is prepared. Then, a mask forming film 21 is formed on the surface of the glass substrate 20. 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 Forming Step> After the mask forming film 21 is formed on the surface of the glass substrate 20, as shown in FIG. 2B, the mask forming film 21 has an initial hole that becomes a mask opening at 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. 2C, 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, that is, the mask as shown in FIG. A recess 24 is formed by etching with an etching solution from a portion where no material is present. By controlling the etching time and gradually etching the glass substrate 20, a recess 24 having a predetermined depth can be formed as shown in FIG. In addition, about this recessed part 24, it is preferable to make the depth as shallow as possible, in order to make thickness of the micro lens 11 to form thin. Therefore, in the present embodiment, the recess 24 is formed in a hemispherical shape so that its depth is about the radius of the hemisphere.

<Mask Removal Step> Thereafter, the mask 23 is removed by etching or the like, whereby a substrate 25 having a large number of recesses 24 as shown in FIG. 2E, that is, the substrate shown in FIGS. 1A and 1B. (Microlens array substrate) 12 is obtained.

[Inorganic Lens Material Filling Step] Next, in the concave portion 24 (lens-shaped concave portion 12a) of the substrate 25 (microlens array substrate 12) obtained in this substrate manufacturing step, shown in FIGS. In this way, the paste-like inorganic lens material (inorganic lens material dispersion) obtained in the above-described inorganic lens material preparation step is filled. That is, the inorganic lens material is filled in the concave portion 24 by a wet method. The reason why the wet method is employed in this way is that the wet method has good embeddability, so that the inorganic lens material can be selectively filled in the recess 24, so that the time required for filling can be made relatively short. . 3A is a plan view schematically showing the substrate 25 viewed from the surface on which the recess 24 is formed, and FIG. 3B is a cross-sectional view taken along the line B-B in FIG. 3 (c) and 3 (d) are explanatory diagrams of the filling process of the inorganic lens material.

First, pretreatment such as cleaning and drying is performed on the substrate 25 having the recesses 24 shown in FIGS. 3A and 3B manufactured in the substrate manufacturing process, if necessary. Next, the paste-like inorganic lens material is filled into the recesses 24 of the substrate 25 by a screen printing method which is a wet method. First, as shown in FIG. 3C, 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 inorganic lens material 31 at the position corresponding to the recess 24. The mesh pattern 30a is determined by the fluidity (viscosity) of the paste-like inorganic lens material 31 and the depth of the recess 24 of the substrate 25. The simplest pattern is a lens forming range. You may form what is called a solid pattern imprinted on the whole surface. The thickness of such a screen printing plate 30 is set depending on the solid content concentration of the inorganic lens material 31. 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 arranging the screen printing plate 30 in this way, the inorganic lens material 31 is arranged on the screen printing plate 30, and then the inorganic lens material 31 is leveled by the squeegee 32. Accordingly, the inorganic lens material 31 can be filled and disposed in and on the concave portion 24 of the substrate 25 by pressing the paste-like inorganic lens material 31.

Here, with respect to the amount of the inorganic lens material 31 to be filled, that is, the thickness thereof, the recess 24 is surely filled, and the polishing allowance for flattening in the flattening step which is a subsequent step is 1 to 5 μm. It is considered to be within a range. By filling the concave lens 24 with the inorganic lens material 31 in this way, as shown in FIG. 3D, a microlens array substrate 33 before firing, which is filled with the inorganic lens material 31, is obtained.

Here, the screen printing method is used as a wet method for filling the recess 24 with the inorganic lens material. However, if the inorganic lens material can be satisfactorily filled in the recess 24, a wet method other than the screen printing method may be used. It can also be adopted. For example, a spin coat method or a dispenser method can be employed by adjusting the viscosity of the dispersion liquid of the inorganic lens material.

[Lens Layer Forming Step] Next, the unfired microlens array substrate 33 shown in FIG. That is, in this firing step, the inorganic lens material 31 filled in the concave portion 24 is heated and fired to form the microlens 11 shown in FIGS. 1 (a) and 1 (b). At this time, in the present embodiment, the baking is performed at a temperature higher than the softening point of the glass frit in the dispersion liquid of the inorganic lens material 31, for example, about 50 ° C. to 100 ° C. higher than the softening point temperature of the glass frit.

Specifically, first, the pre-firing microlens array substrate 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 substrate 33 is fired in a firing furnace such as an electric furnace. 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 the binder removal treatment is performed 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. Then, the heating temperature (firing temperature) is maintained for about 15 minutes to 60 minutes, and the glass frit is softened to be vitrified. For example, when a borosilicate glass frit is used as the glass frit, the softening point temperature is 780 ° C., so the heating temperature is increased to 850 ° C.

Thereafter, the microlens array substrate is returned to room temperature by natural cooling. Thereby, the microlens layer 13 which formed the microlens 11 in the recessed part 12a (recessed part 24) 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 inorganic lens material 31.

[Planarization Step] The microlens layer 13 obtained in this way is a sufficiently flat surface because the surface on the side opposite to the recess 24 is smoothed by the squeegee 32 and further baked. Not. Therefore, the microlens layer 13 is flattened as shown in FIG. As the planarization treatment, a polishing method or a CMP method (chemical mechanical polishing method) is preferably used.

At that time, as shown in FIG. 4B, the microlens layer 13 is flattened until at least a part of the substrate 25 (substrate 12) is exposed. That is, planarization is performed so that the substrate surface between the recesses 24 and 24 is exposed. Thereby, the final thickness of the obtained microlens layer 13 can be made sufficiently thin. In addition, the microlenses 11 formed in the recesses 24 (recesses 12a) can be individually made independent of each other. In addition, Fig.4 (a) is CC sectional view taken on the line of FIG.4 (b).

[Optical Path Length Adjusting Film Forming Step] Next, as shown in FIG. 4C, an optical path length adjusting film 14 is formed on the microlens layer 13 after the flattening process by a vapor deposition method. As the vapor deposition method, a chemical vapor deposition method (CVD method) or a physical vapor deposition method (PVD method) such as a vapor deposition method or a sputtering method is employed. Among these vapor deposition methods, the chemical vapor deposition method has a high film density and is a general method for forming an optical film. Further, the vapor deposition method has a high film formation rate, and the sputtering method has an advantage that the film formation apparatus is relatively simple and inexpensive. Accordingly, a film forming method is appropriately selected from the advantages of each of these film forming methods and the optical path length adjusting film 14 is formed. Thereby, the microlens array 10 shown in FIGS. 1A and 1B is obtained.

In this embodiment, since the film density is particularly high and a film having high characteristics can be obtained as an optical film, a CVD method such as a plasma CVD method or a thermal CVD method is preferably employed. The optical path length adjusting film 14 to be formed, that is, the CVD film, is preferably a film having a thermal expansion coefficient smaller than that of the microlens layer 13. As such a CVD film, a SiO ₂ film is preferably used. The thermal expansion coefficient (linear expansion coefficient α) of the SiO ₂ film is approximately 10 × 10 ⁻⁷ / ° C., although it varies depending on the film forming material and the film forming conditions. Compared with glass (about 30 × 10 ⁻⁷ / ° C.), it is sufficiently small.

The thickness of the optical path length adjusting film 14 is not particularly limited and is set to a preset thickness. In other words, the optical path length adjusting film 14 has almost no function as a lens and is merely a film for adjusting the optical path length so that the focal point is at the optimum position. Therefore, the optical path length adjusting film 14 is not required to have a particularly high refractive index, and may be, for example, approximately the same as the microlens array substrate 25.

Since the optical path length adjusting film 14 obtained in this way is formed by a vapor phase film forming method that easily reflects the shape of the base, the lens layer 13 after the planarization as the base and the exposed substrate 25 are exposed. Reflecting the flat surface formed by the above, a flat film is formed. Therefore, the planarization process can be omitted for the optical path length adjusting film 14, and the microlens array 10 shown in FIGS. 1A and 1B can be used as it is.

In the method for manufacturing the microlens array 10 of the present embodiment, the step of forming the microlens layer 13 in the recess 24 and the step of forming the optical path length adjusting film 14 on the microlens layer 13 are separated. Therefore, the inorganic lens material for forming the microlens layer 13 and the material for forming the optical path length adjusting film can be separated. Therefore, compared with the case where the microlens layer 13 and the optical path length adjusting film 14 are formed integrally, the thickness of only the microlens layer 13 can be sufficiently reduced.

Since the thickness of the microlens layer 13 can be reduced, even if the difference in thermal expansion coefficient between the microlens layer 13 and the substrate (microlens array substrate) 25 increases, the thickness of the microlens layer 13 can be reduced. The effect of the difference in thermal expansion coefficient can be reduced by the thickness. Therefore, in this embodiment, in particular, the microlens layer 13 is formed thin, thereby reducing the influence of the difference in thermal expansion coefficient between the microlens layer 13 and the substrate 25 and suppressing the occurrence of cracks and warpage. Therefore, although a quartz glass substrate or a neo-ceram glass substrate having a small thermal expansion coefficient is used as the substrate 25, an inorganic lens material having a relatively large thermal expansion coefficient as compared with these substrates is used to form a microlens. Layer 13 can be formed. That is, a lens material having a high refractive index and a high transmittance can be appropriately selected and used, and therefore the degree of freedom in selecting a lens material to be used can be increased. In addition, since a lens material having a high refractive index and high transparency can be used, the microlens array 10 having the microlenses 11 having excellent optical characteristics can be manufactured.

Moreover, since the filling of the inorganic lens material is performed by a wet method with good embedding properties, the microlens layer 13 can be formed in a relatively short time including the subsequent firing step, and thus the productivity can be improved. . In particular, since the screen printing method is adopted as the wet method, the manufacturing cost can be greatly reduced as compared with the case where the vapor deposition method such as the CVD method is used. Furthermore, since the optical path length adjusting film 14 is formed by a vapor phase film forming method that easily reflects the shape of the base, the obtained optical path length adjusting film 14 is the microlens layer 13 or the substrate 25 after the planarization process as the base. Reflecting the flat surface, a flat film is formed. Therefore, the planarization process can be omitted for the optical path length adjusting film 14.

In the flattening step, the microlens layer 13 is flattened until at least a part of the substrate 25 (substrate 12) is exposed. Therefore, the thickness of the microlens layer 13 is reduced and the microlens layer 13 and the substrate are thinned. The influence by the difference in thermal expansion coefficient from 25 can be further reduced. Further, since the microlenses 11 formed in the recesses 24 (recesses 12a) can be made independent of each other without being continuous with each other, the transmission of stress between these microlenses 11 is prevented and the generation of cracks is suppressed. can do.

Further, since the thermal expansion coefficient of the optical path length adjusting film 14 is smaller than the thermal expansion coefficient of the microlens layer 13, the thermal expansion coefficient is reduced by the substrate 25 and the optical path length adjusting film 14 having a relatively small thermal expansion coefficient. Since the relatively large microlens layer 13 is sandwiched, the microlens layer 13 can be pressed from both the upper and lower sides even when a thermal load is applied, thereby causing cracks in the microlens layer 13 and its periphery, It is possible to suppress warping of the microlens array 10.

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.

Second Embodiment FIGS. 5A and 5B are diagrams showing a schematic configuration of a second embodiment of a microlens array according to the present invention. FIG. 5A is a plan view, and FIG. It is DD sectional view taken on the line of a). In FIGS. 5A and 5B, reference numeral 40 denotes a microlens array. The microlens array 40 is mainly different from the microlens array 10 shown in FIGS. 1A and 1B in that the microlens 41 is different from the first lens layer 42 as shown in FIG. The second lens layer 43 has a laminated structure.

That is, the microlens array 40 includes a first lens layer 42 and a second lens layer 43 on a substrate (microlens array substrate) 12 on which a plurality of concave portions (lens-shaped concave portions) 12 a corresponding to the plurality of microlenses 41 are formed. Are laminated, and a microlens layer 44 composed of the plurality of microlenses 41 is formed.
And an optical path length adjusting film 14 is formed on the microlens layer 44 and the substrate 12.

As a second embodiment of the method for manufacturing a microlens array according to the present invention, a method for manufacturing the microlens array 40 having such a configuration will be described. First, in order to form the microlens 41 by a wet method, a first inorganic lens material dispersion for forming the first lens layer 42 and a second inorganic lens material for forming the second lens layer 43 are used. Each of the dispersions is prepared.

As materials, both the dispersion liquid of the first inorganic lens material and the dispersion liquid of the second inorganic lens material are the same as the dispersion liquid of the inorganic lens material prepared in the first embodiment. However, in this embodiment, the refractive index of the obtained first lens layer 42 is higher than the refractive index of the substrate 12 (microlens array substrate), and the refractive index of the second lens layer 43 is the refractive index of the first lens layer 42. The first inorganic lens material (glass frit) and the second inorganic lens material (glass frit) are selected so as to be higher than the ratio.

That is, as the first inorganic lens material (glass frit), a material having a refractive index higher than the refractive index of the microlens array substrate 13 is used as a material that finally becomes the first lens layer 42. As the second inorganic lens material (glass frit), the refractive index is that of the first lens layer 42, that is, the first inorganic lens material (glass frit). Those having a refractive index higher than that are used.

For the first lens layer 42 and the second lens layer 43, it is preferable that the thermal expansion coefficient of the second lens layer 43 is smaller than the thermal expansion coefficient of the first lens layer 42. Therefore, as the glass frit for forming the first lens layer 42 and the second lens layer 43, those satisfying the above conditions for the thermal expansion coefficient in addition to the conditions for the refractive index are preferably used. That is, as the glass frit for the second lens layer 43, one having a thermal expansion coefficient smaller than that of the glass frit for the first lens layer 42 is preferably used.

In addition, about the glass frit for the 1st lens layer 42, the thing with the thermal expansion coefficient larger than the board | substrate 12 (board | substrate 25) can be used like 1st Embodiment. In addition, as the glass frit for the second lens layer 43, one having a thermal expansion coefficient larger than that of the substrate 12 (substrate 25) can be used. Of the glass frit mentioned in the embodiment, those satisfying both the refractive index and thermal expansion coefficient conditions are appropriately selected and used.

After selecting the glass frit for the first inorganic lens material and the glass frit for the second inorganic lens material, each was prepared in the same manner as in the first embodiment to prepare a paste-like dispersion, and the first inorganic frit was used. A lens material dispersion and a second inorganic lens material dispersion are respectively formed. Then, the dispersion liquid of each inorganic lens material obtained in this way is formed into a concave portion of the substrate 25 by the same wet method as in the first embodiment, that is, the screen printing method shown in FIGS. 24 is filled.

At that time, first, the filling amount (application amount) of the dispersion liquid of the first inorganic lens material is adjusted so as to fill a part (a little more than half) without filling the entire concave portion 24 of the substrate 25. To fill. Subsequently, the first inorganic lens material is baked under the same conditions as in the first embodiment. Thus, the first lens layer 42 is formed in the recess 24 as shown in FIG.

Next, a second inorganic lens material is filled on the first lens layer 42 in the recess 24. And this 2nd inorganic lens material is baked on the conditions similar to 1st Embodiment. Thus, the second lens layer 43 is formed on the first lens layer 42 in the recess 24 as shown in FIG. The first lens layer 42 and the second lens layer 43 thus formed can refract incident light twice by being laminated. In other words, the microlens 41 formed by the first lens layer 42 and the second lens layer 43 has a function of refracting twice, so that it becomes highly refractive.

Thereafter, in the same manner as in the first embodiment, a step of flattening the microlens 41 is performed as shown in FIG. 6C, and the optical path length adjusting film 14 is formed as a vapor deposition method as shown in FIG. By forming by (CVD method), the microlens array 40 shown in FIG. 5 is obtained. Note that the thickness of the first lens layer 42 and the thickness of the second lens layer 43 are not particularly limited to the forms shown in FIGS. 6A to 6D, and the thickness of each lens material (glass frit) is not limited. It is determined appropriately according to the type and design of the finally obtained liquid crystal panel. For example, as shown in FIGS. 7A to 7C, the thickness of the first lens layer 42 may be reduced and the thickness of the second lens layer 43 may be increased. Such adjustment of the thickness can be easily performed by adjusting the amount when each lens material is filled (applied).

In the method for manufacturing the microlens array 40 of the present embodiment, the thickness of the first lens layer 42 and the thickness of the second lens layer 43 are formed thinner than the entire thickness of the microlens lens layer 44, respectively. Therefore, the influence of the difference in thermal expansion coefficient between the first lens layer 42 and the substrate 12 and the influence of the difference in thermal expansion coefficient between the second lens layer 43 and the substrate 12 can be reduced. Therefore, generation of cracks and warpage can be suppressed. Further, by combining inorganic lens materials (glass frit) having different refractive indexes, the lens characteristics of the obtained microlens lens layer 44 can be enhanced. Furthermore, the light can be efficiently condensed at the center by optically reducing the refraction near the center of the lens and increasing the refraction near the outer periphery.

Further, since the thermal expansion coefficient of the second lens layer 43 is configured to be smaller than the thermal expansion coefficient of the first lens layer 42, the substrate 12 (microlens array substrate) having a relatively small thermal expansion coefficient is used. Since the first lens layer 42 having a relatively large thermal expansion coefficient is sandwiched between the second lens layer 43 and the first lens layer is pressed from both sides even when a thermal load is applied, cracks and warping are caused. Occurrence is suppressed. Further, if the first lens layer 42 having a smaller coefficient of thermal expansion than the second lens layer 43 is formed thinner than the second lens layer 43 as shown in FIGS. The influence of the difference in thermal expansion coefficient between the lens layer 42 and the substrate 12 can be further reduced, and the occurrence of cracks and warpage can be suppressed.

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. 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. 8 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. 9 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 is maintained by applying the microlens array of the present invention while being a device that receives light from the light source 61 in FIG. 8 and is in a very high temperature environment and easily deforms due to linear expansion. It has become so.

DESCRIPTION OF SYMBOLS 10 ... Micro lens array, 11 ... Micro lens, 12a ... Recessed part (lens-shaped recessed part), 12 ... Substrate (micro lens array substrate), 13 ... Micro lens layer (lens layer), 14 ... Optical path length adjustment film, 20 ... Glass Substrate, 24 ... concave portion, 25 ... substrate (microlens array substrate), 30 ... screen printing plate, 31 ... inorganic lens material, 32 ... squeegee, 33 ... microlens array substrate before firing, 40 ... microlens array, 41 ... Microlens, 42 ... first lens layer, 43 ... second lens layer, 44 ... microlens layer

Claims (6)

A step of filling the lens-shaped recesses of the microlens array substrate having the lens-shaped recesses with an inorganic lens material by a wet method, and firing the inorganic lens material to form a lens layer that fills at least the lens-shaped recesses. And a step of flattening the lens layer, and a step of forming an optical path length adjusting film on the lens layer after the flattening by a vapor deposition method. . In the step of filling the inorganic lens material by a wet method, a first inorganic lens material having a refractive index higher than that of the microlens array substrate is filled in the lens-shaped recess by a wet method, and then the first inorganic lens material is filled. Is fired to form a first lens layer, and then a second inorganic lens material having a refractive index higher than that of the first inorganic lens material is filled on the first lens layer in the lens-shaped concave portion by a wet method. The method of manufacturing a microlens array according to claim 1. 3. The microlens array according to claim 2, wherein the second lens layer formed by firing the second inorganic lens material has a thermal expansion coefficient smaller than that of the first lens layer. Method. The method of manufacturing a microlens array according to any one of claims 1 to 3, wherein a thermal expansion coefficient of the optical path length adjusting film is smaller than a thermal expansion coefficient of the lens layer. The method for producing a microlens array according to any one of claims 1 to 4, wherein in the step of flattening, the lens layer is flattened until at least a part of the microlens array substrate is exposed. . The microlens array manufactured by the manufacturing method as described in any one of Claims 1-5.

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