HK1179349A - Method for producing wavelength plate - Google Patents

Description

Method for manufacturing wavelength plate

Technical Field

The present invention relates to a method for manufacturing a wavelength plate having birefringence caused by a birefringent layer formed by oblique deposition.

The present application claims priority based on japanese patent application No. 2010-144559, filed in japan on 25/6/2010, which is incorporated by reference in the present application.

Background

Conventionally, most of wavelength plates have been made of inorganic optical single crystals such as quartz or polymer stretched films. However, although the inorganic optical single crystal is excellent in performance, durability, and reliability as a wavelength plate, it is expensive in raw material cost and processing cost. In addition, the polymer stretched film is easily deteriorated by heat and UV light, and is not excellent in durability.

For this reason, for example, optical elements have been proposed as disclosed in patent documents 1 to 4, in which particles are deposited in a direction inclined with respect to a substrate surface to form an inclined columnar structure and which have birefringence with respect to light rays incident perpendicularly to the substrate surface. The oblique deposition wavelength plate on which the oblique deposition film having the oblique columnar structure is formed can set an arbitrary phase difference by adjusting the film thickness in principle. In addition, the area can be relatively increased, and the cost can be reduced by mass production.

The obliquely deposited film described in patent document 1 is composed of at least 2 layers of a material exhibiting high wavelength dispersion in retardation and a material exhibiting low wavelength dispersion deposited obliquely, and is suitable for a wavelength plate in a wide band of visible light. In the oblique deposition film of patent document 1, a material exhibiting high wavelength dispersion in phase difference and a material exhibiting low wavelength dispersion are used, and the layers are stacked so that the deposition directions of the dielectric materials of the layers with respect to the substrate are different, and the slow axis of the deposition film is perpendicular.

In addition, patent document 2 describes an optical retarder having high durability and high stability by using an oblique deposition of a birefringent layer having a dense structure. Patent document 3 describes a polarizer for holograms for optical pickup which is produced by obliquely depositing a high refractive material on a one-dimensional grid. In addition, the photonic crystal wavelength plate described in patent document 4 can set a wide operating wavelength by using an alternating multilayer film of a high refractive index medium layer and a low refractive index medium layer having a periodic uneven shape.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 11-23840;

patent document 2: japanese patent laid-open publication No. H2007-188060;

patent document 3: japanese patent laid-open publication No. 11-250483;

patent document 4: WO 2004/113974 publication.

Disclosure of Invention

Problems to be solved by the invention

The wavelength plate having such an obliquely deposited film formed thereon is required to have high moisture resistance in order to obtain high durability and high stability. However, since the wavelength plate on which the obliquely deposited film is formed has a columnar structure, moisture easily enters gaps between materials, and there is a problem that moisture resistance is deteriorated.

The present invention has been made in view of the above-described conventional circumstances, and an object of the present invention is to provide a method for manufacturing a wavelength plate having a birefringence due to a birefringent layer formed by oblique deposition, having high moisture resistance, and being excellent in durability and stability.

Means for solving the problems

The present inventors repeated various studies and found that: by forming a protective film of low moisture permeability on microparticles deposited on a substrate by oblique deposition, a wavelength plate having high moisture resistance, excellent durability and excellent stability can be manufactured.

That is, the present invention provides a method for manufacturing a wavelength plate, comprising: a birefringent layer forming step of depositing a dielectric material on a substrate in a tilted manner to form a birefringent layer having columnar portions in which microparticles of the dielectric material are stacked in columnar form and gap portions provided between the columnar portions; an annealing step of annealing the birefringent layer at a temperature of 100 ℃ to 300 ℃; and a protective film forming step of forming a protective film by forming an inorganic compound on the annealed birefringent layer at a high density.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the method for manufacturing a wavelength plate of the present invention, a wavelength plate having high moisture resistance, excellent durability and excellent stability can be manufactured.

Drawings

Fig. 1 is a diagram for explaining shape anisotropy of fine particles of a dielectric material.

Fig. 2 is a schematic cross-sectional view of a wavelength plate according to an embodiment of the present invention.

Fig. 3 is a schematic cross-sectional view of a wavelength plate according to an embodiment of the present invention.

Fig. 4A and 4B are diagrams illustrating examples of the structures of the substrates, respectively.

Fig. 5 is a schematic cross-sectional view of a wavelength plate according to an embodiment of the present invention.

Fig. 6 is a schematic cross-sectional view of a wavelength plate according to an embodiment of the present invention.

Fig. 7 is a sectional view showing a main part of a wavelength plate according to an embodiment of the present invention.

Fig. 8 is a flowchart illustrating a method for manufacturing a wavelength plate according to an embodiment of the present invention.

Fig. 9 is a diagram for explaining an outline of oblique deposition.

FIG. 10 is a graph showing the transmittance immediately after completion of the sample of the wavelength plate in example 1 and the transmittance after 100-hour retention in the moisture resistance load test.

Fig. 11 is a graph showing the transmittance of the wavelength plate when the annealing temperature is changed.

FIG. 12 is a graph showing the transmittance immediately after completion of the sample of the wavelength plate in comparative example 1 and the transmittance after 100-hour retention in the moisture resistance load test.

FIG. 13 is a graph showing the transmittance immediately after completion of the sample of the wavelength plate in comparative example 2 and the transmittance after 100-hour retention in the moisture resistance load test.

Fig. 14 is a graph showing a comparison of birefringence amounts of a wavelength plate using a one-dimensional checkered substrate and a wavelength plate using a flat substrate.

Fig. 15 is a diagram showing an SEM image of a cross section of a wavelength plate using a one-dimensional checkered substrate.

Detailed Description

Hereinafter, embodiments of the present invention (hereinafter referred to as "the present embodiments") will be described in detail in the following order with reference to the drawings.

1. Method for manufacturing wavelength plate

2. Modification example

2-1. Modification example 1

2-2. Modification 2

2-3. Modification 3

3. Treatment procedure

4. Examples of the embodiments

< 1. method for manufacturing wavelength plate

The method for manufacturing a wavelength plate according to the present embodiment is a method for manufacturing a wavelength plate in which the amount of birefringence is increased by the birefringence of fine particles due to oblique deposition, in which a dielectric material is obliquely deposited on a transparent substrate to form a birefringent layer (obliquely deposited film), then, moisture in the birefringent layer is evaporated by annealing treatment, and thereafter, an inorganic compound is formed on the birefringent layer at high density to form a protective film having low moisture permeability. The birefringence of the particles caused by the oblique deposition is found, for example, as shown in fig. 1, by a difference in refractive index between the long axis direction n1 and the short axis direction n2 due to the shape anisotropy of the particles of the dielectric material.

In the method of manufacturing a wavelength plate according to the present embodiment, for example, a wavelength plate shown in a cross-sectional view of fig. 2 is manufactured. The wavelength plate shown in fig. 2 is formed by depositing a dielectric material obliquely from 1 direction on a substrate 11 to form columnar portions 12. Thereby, the gap portion 13 is formed between the plurality of pillar portions 12. The birefringent layer 14 including the columnar portions 12 and the gap portions 13 is subjected to annealing treatment to evaporate water in the gap portions 13. Then, the protective film 15 is formed by forming an inorganic compound in the birefringent layer 14 at a high density.

As the substrate 11, a transparent substrate such as a glass substrate, a silicon substrate, or a plastic substrate can be used. Among them, quartz glass (SiO) which absorbs little in the visible light region (wavelength region: 380nm to 780nm) is preferable₂) A substrate.

As the substrate, glass was usedAmong transparent substrates such as substrates, silicon substrates and plastic substrates, quartz glass (SiO) which absorbs little in the visible light region (wavelength region: 380nm to 780nm) is preferably used₂) A substrate. In addition, a substrate having an antireflection film formed on one surface thereof may be used. In this case, as the antireflection film, for example, a multilayer thin film including a general high refractive film and a low refractive film can be formed.

The columnar portion 12 is formed by stacking fine particles by oblique deposition of a dielectric material. As the dielectric material, Ta-containing materials can be used₂O₅、TiO₂、SiO₂、Al₂O₃、Nb₂O₅、MaF₂Etc. of high refractive material. Among them, Ta having a refractive index of 2.25 is preferably contained₂O₅Of a high refractive material.

The columnar portion 12 is formed by obliquely depositing a dielectric material in the xy plane with the xy plane in the x, y, z vertical coordinates as the substrate plane. The oblique deposition is performed at a deposition angle of, for example, 60 ° to 80 ° with respect to the z-axis, and a layer of particles is formed in the z-axis direction.

The gap portion 13 is an air layer provided between the columnar portions 12. The gap 13 is formed by a so-called self-shielding effect in which fine particles of the dielectric material fly in an oblique direction, and therefore, a dark place where the dielectric material cannot be directly attached appears. Since the gap portion 13 is an air layer provided in an oblique direction, there is a problem that: in the wavelength plate having the birefringent layer formed by the conventional oblique deposition, for example, moisture in the gap portion 13 such as moisture adsorbed on the side surface of the columnar portion 12 is less likely to evaporate to the outside of the birefringent layer 14, and the humidity resistance is low.

Therefore, in the present embodiment, the birefringent layer 14 is annealed to evaporate water present inside the gap portion 13, and then the protective film 15 having low humidity permeability is formed on the birefringent layer 14. Thus, a wavelength plate exhibiting excellent resistance to external humidity is realized.

The annealing treatment is preferably carried out at a temperature of 100 ℃ or higher at which water is evaporated. Further, if the temperature of the annealing treatment is too high, columnar structures may grow to form columnar structures, and a decrease in birefringence, a decrease in transmittance, and the like may occur, and therefore, 300 ℃.

As a material of the protective film 15, for example, SiO having low moisture permeability is preferably used₂、Ta₂O₅、TiO₂、Al₂O₃、Nb₂O₅、LaO、MgF₂And the like. In addition, since the polymer material has poor heat resistance, it is not preferable as a material of the protective film 15.

As a method for forming the protective film 15, a method is used in which a protective film having low moisture permeability can be formed by forming such an inorganic compound at high density. The method of forming the protective film 15 may, for example, be a Chemical Deposition (CVD) method. When the protective film 15 is formed by the CVD method, the film is set to atmospheric pressure to medium vacuum (100 to 10)^－1Pa) inside the container, the substrate having the birefringent layer 14 formed thereon is placed, and the material of the protective film 15, i.e., the gaseous inorganic compound, is fed into the container, and energy such as heat, plasma, light, etc. is supplied to cause the gaseous inorganic compound to chemically react with the birefringent layer 14. According to such a CVD method, an inorganic compound can be formed as the protective film 15 having low moisture permeability on the birefringent layer 14 at high density.

Instead of such a CVD method, any method capable of forming an inorganic compound with high density, such as a plasma-assisted deposition method or a sputtering method, may be used to form the protective film 15.

The manufactured wavelength plate 1 has high moisture resistance and realizes excellent durability and stability by increasing the amount of birefringence by the fine particles deposited on the substrate 11 by oblique deposition and forming the protective film 15 having low moisture permeability on the fine particles.

< 2. modification example >

In the present embodiment, for example, a wavelength plate having the structure shown in fig. 3, 5, and 6 may be manufactured instead of the structure shown in fig. 2. In the configurations shown in fig. 3, 5, and 6, the same configurations as those in fig. 2 will not be described.

(2-1. modified example 1)

The wavelength plate 2 shown in fig. 3 increases the amount of birefringence by the birefringence of the fine particles caused by oblique deposition and also by the birefringence caused by the microstructure. The birefringence due to the microstructure is found, for example, by shape anisotropy of a fine pattern of periodic concavities and convexities formed on a substrate of a medium.

In the manufacture of the wavelength plate 2, a fine pattern including periodic projections 24 and recesses 25 at a wavelength of light or less is formed on the substrate 21. Then, the fine particles of the dielectric material are stacked in a columnar shape on the convex portions 24 by the oblique deposition of the dielectric material from 1 direction to form the columnar portions 22. Thereby, the gap portion 23 is formed between the columnar portions 22 on the concave portion 25. Then, the birefringent layer 26 including the columnar portions 22 and the gap portions 23 is annealed under the above-described conditions, so that the water present in the gap portions 23 is evaporated. Then, an inorganic compound is formed on the birefringent layer 26 at a high density by a CVD method or the like, thereby forming the protective film 27 having low moisture permeability.

In this way, by forming the columnar portions 22 on the convex portions 24 of the substrate 21 and forming the wavelength plates 2 of the gap portions 23 on the concave portions 25 of the substrate 2, the amount of birefringence can be further increased by utilizing birefringence due to fine particles of the dielectric material and birefringence due to irregularities of the substrate 21. Further, by using a composition containing Ta₂O₅The high refractive index material of (2) can be used as a dielectric material to form a wavelength plate having a birefringence of 0.13 or more in the visible light region.

Fig. 4A and 4B are a plan view and a cross-sectional view respectively showing a configuration example of the substrate 21. When the xy plane in the x, y, z vertical coordinates is taken as the substrate plane, the substrate 21 is patterned with a period (pitch) equal to or less than the wavelength of light and a predetermined depth in the x-axis direction with the convex portions 24 and the concave portions 25. That is, one-dimensional squares (grids) having refractive indices different in the major axis direction n1 and the minor axis direction n2 due to the optical path difference of the uneven structure are formed on the substrate 21.

On the convex portions 24 constituting the fine pattern having a pitch of a wavelength or less, a dielectric material is deposited by oblique deposition perpendicular to the gridlines and with a deposition source at a predetermined angle with respect to the normal direction of the substrate surface. This can increase the amount of birefringence of the wavelength plate, as compared with the case where the dielectric material is directly deposited on a flat substrate (hereinafter, also referred to as a "flat substrate") on which no fine pattern is formed.

By combining the fine pattern with the birefringent film formed by oblique deposition in this way, it is possible to realize a thinner wavelength plate in which the amount of birefringence is increased and desired phase characteristics are obtained. The thinning has many advantages such as speeding up and making the production process efficient, and suppressing the cost of materials used for film formation. In this way, it is considered that the formation of the birefringent film on the fine pattern increases the amount of birefringence, and the effect of structural birefringence is increased by the presence of the space between the one-dimensional cells.

As a method for forming a fine pattern, a fine pattern having a pitch of a wavelength or less may be formed, and examples thereof include a random pattern, a pattern forming method using a block copolymer described in non-patent document 1 (toshiba review-vol 60 No 102005), and the like, in addition to the above-described one-dimensional checkers. The pattern forming method of non-patent document 1 is to form SiO on a glass substrate by, for example, CVD method₂A film patterned with a block copolymer, the pattern of the block copolymer being transferred to SiO₂。

In addition, SiO may not be formed on the glass substrate₂The film is directly formed into a fine pattern. Even in the wavelength plate having the fine pattern formed as described above, a wavelength plate having high moisture resistance and excellent stability can be obtained by forming a protective film having low moisture permeability on the deposited film.

(2-2. modification 2)

The wavelength plate 3 shown in fig. 5 increases the amount of birefringence by the birefringence of the particles caused by oblique deposition from different 2 directions. In the manufacture of the wavelength plate 3, microparticles of a dielectric material are stacked on the substrate 31 by oblique deposition from 2 different directions, and the columnar portion 32 including the microparticle layers 32a and 32b is formed. Thereby, the gap 33 is formed between the columnar portions 32. Then, the birefringent layer 34 including the columnar portions 32 and the gap portions 33 is annealed under the above-described conditions, so that the water present inside the gap portions 33 is evaporated. Then, an inorganic compound is formed on the birefringent layer 34 at a high density by a CVD method or the like, thereby forming the protective film 35 having low moisture permeability.

The columnar portion 32 sequentially deposits the dielectric material obliquely from 2 directions differing by 180 ° in the xy plane with the xy plane in the x, y, z vertical coordinates as the substrate plane. That is, the columnar portion 32 is formed by stacking the fine particle layers 32a and 32b in this order on the substrate 31. The oblique deposition is performed sequentially from 2 directions different by 180 ° at deposition angles of, for example, 60 ° to 80 ° with respect to the z-axis, and a layer of particles is formed in the z-axis direction. Here, an operation of performing the oblique deposition from the other direction by rotating the substrate 31 by 180 ° after performing the oblique deposition from the one direction is taken as 1 cycle. By performing this cycle a plurality of times, a multilayer film deposited from 2 directions can be obtained.

The thickness of each layer (fine particle layers 32a, 32b) of the columnar portion 32 is preferably 50nm or less, more preferably 10nm or less, and thus, by making the thickness of the fine particle layers 32a, 32b thin, even when the number of layers of the fine particle layers is further increased, a columnar shape extending straight in the z-axis direction can be obtained, and the amount of birefringence can be further increased.

(2-3. modification 3)

The wavelength plate 4 shown in fig. 6 increases the amount of birefringence due to the birefringence of the fine particles caused by the oblique deposition from the different 2 directions, and also increases the amount of birefringence due to the birefringence caused by the microstructure. The birefringence due to the microstructure is found, for example, by shape anisotropy due to irregularities formed on a substrate of the medium.

In the manufacture of the wavelength plate 4, periodic projections 44 and recesses 45 are formed on the substrate 41 at a wavelength of light or less. Then, microparticles of a dielectric material are layered on the convex portions 44 by oblique deposition from 2 different directions, and the columnar portions 42 including the microparticle layers 42a, 42b are formed. Thereby, the gap portion 43 is formed between the columnar portions 42 on the concave portion 45. Then, the birefringent layer 46 including the columnar portions 42 and the gap portions 43 is annealed under the above-described conditions, so that the water present inside the gap portions 43 is evaporated. Then, an inorganic compound is formed on the birefringent layer 46 at a high density by a CVD method or the like, thereby forming the protective film 47 having low moisture permeability.

According to the wavelength plate 4 having the columnar portion 46 formed in the direction perpendicular to the substrate surface on the convex portion 44 of the substrate 41 and the gap portion 43 formed on the concave portion 45 of the substrate 41, the amount of birefringence can be increased by the birefringence of the fine particles caused by the oblique deposition from the different 2 directions, and also by the birefringence caused by the uneven microstructure of the substrate 41. Further, by using a composition containing Ta₂O₅The high refractive index material of (2) can be used as a dielectric material for a wavelength plate having a birefringence of 0.13 or more in the visible light region and an excellent wavelength dispersion (wavelength dependence) in which the difference between the birefringence of arbitrary 2 wavelengths in the visible light region is 0.02 or less.

In the examples shown in fig. 5 and 6, for the sake of simplicity of explanation, the columnar portion including 2 fine particle layers is formed by performing the oblique deposition in which the dielectric material is obliquely deposited in order from 2 directions different by 180 ° for 1 cycle, but the number of fine particle layers is not limited thereto, and may be several to several hundred layers. As the number of layers of the fine particles increases, the birefringence of the wavelength plate can be further increased. For example, as shown in fig. 7, oblique deposition in which a dielectric material is obliquely deposited in order from 2 directions different by 180 ° is performed for 4 cycles on the convex portions 44 formed on the substrate 41, thereby forming the columnar portions 48 in which 8 fine particle layers are stacked in the direction perpendicular to the substrate on the convex portions 44, and forming the birefringent layer 49 including the columnar portions 48 and the gap portions 43. Thus, a wavelength plate having a further increased birefringence can be obtained as compared with a wavelength plate having a smaller number of fine particle layers.

In this way, by combining the fine pattern with the birefringent layer (obliquely deposited film) including the plurality of fine particle layers, the film thickness can be made thin and the amount of birefringence can be further increased. In the wavelength plate manufactured in this way, a protective film having low moisture permeability is formed on the obliquely deposited film, whereby a wavelength plate exhibiting high moisture resistance and excellent stability can be obtained.

In particular, as the number of the deposition medium material particles increases while being tilted in order from 2 directions different by 180 °, the structure of the gap portion becomes complicated, and the moisture adsorbed on the side surface of the columnar portion becomes further difficult to evaporate. The annealing treatment is very effective as a method for evaporating water in the gap portion having a complicated structure as described above.

The substrate of the wavelength plate may be provided with antireflection films (AR) on both surfaces or one surface thereof. Generally, a wavelength plate formed by depositing fine particles on a glass substrate by an oblique deposition method is formed with an antireflection film for the purpose of improving transmittance. As the antireflection film, for example, a multilayer thin film including a high refractive film and a low refractive film which are generally used can be mentioned. By providing the substrate with the antireflection film, the surface reflection of the substrate can be reduced, and the transmittance can be increased. In addition, in order to improve the transmittance, the protective film may be configured to also serve as at least a part of an antireflection film including a multilayer thin film.

For example, in the formation of SiO₂(refractive index 1.5) as a protective film, in a multilayer thin film in which an antireflection film includes a high refractive film and a low refractive film, the protective film can function as a low refractive film. And TiO with a higher refractive index than that₂An inorganic compound having a high refractive index (refractive index 2.4) and formed of SiO₂The low refractive film formed of the protective film functions as a high refractive film.

< 3. Process sequence

Fig. 8 is a flowchart showing an example of the processing steps of the method for manufacturing a wavelength plate according to the present embodiment. First, in step S1, a fine pattern of periodic projections and recesses is formed on the substrate at a wavelength of light or less. Specifically, when an xy plane in x, y, and z vertical coordinates is used as a substrate surface, a fine pattern including convex portions and concave portions, that is, a one-dimensional lattice (grid) in which optical path differences are generated due to irregularities, is formed in the x-axis direction at a period (pitch) equal to or less than the wavelength of light.

As a method for forming a fine pattern, SiO is deposited on a substrate by CVD₂Photolithography is then used to form the photoresist pitch pattern. Then, using CF₄Vacuum etching as a reactive gas to form SiO₂The fine pattern of (2). In the case of manufacturing a wavelength plate in which the fine pattern shown in fig. 2 and 5 is not formed, step S1 is omitted.

Next, in step S2, a dielectric material is deposited on a substrate on which periodic convex and concave portions equal to or less than the wavelength of useful light are formed, for example, with a gradient at a deposition angle of 60 ° to 80 °, thereby forming a birefringent film.

Fig. 9 is a diagram for explaining an outline of oblique deposition. The oblique deposition is performed by providing the deposition source 6 in a direction of a deposition angle α with respect to a normal direction of the substrate surface 51, and the birefringence amount of the deposited film is controlled by changing the deposition angle α. For example, in the presence of Ta₂O₅When the high refractive index material of (2) is used as the dielectric material, the amount of birefringence can be increased by setting the deposition angle α to 60 ° to 80 °.

The dielectric material can be deposited from a direction perpendicular to the lines of the periodic projections and recesses, i.e., the lines of the one-dimensional squares, on the substrate 51, thereby increasing the amount of birefringence.

In the case of multilayer deposition, the dielectric material may be deposited obliquely from 2 directions different by 180 ° in the xy plane when the xy plane in the x, y, z vertical coordinate is taken as the substrate plane, to produce the multilayer fine particle layer shown in fig. 5 and 6. For example, by performing a plurality of cycles of an operation of performing oblique deposition from one direction, then rotating the substrate by 180 ° and performing oblique deposition from the other direction, a multilayer film deposited from 2 directions can be obtained.

Further, by setting the thickness of each layer to 50nm or less, more preferably 10nm or less, and performing a plurality of cycles of deposition, a columnar shape extending in the z-axis direction can be obtained, and the amount of birefringence can be increased.

In step S3, the substrate on which the birefringent film is formed in step S2 is cut into a predetermined size. In cutting, a cutting device such as a glass cutter is used.

In step S4, a protective film is formed on the birefringent film by CVD with respect to the substrate cut in step S3 on which the birefringent film is formed. In step S4, an antireflection film may be further formed on the protective film formed on the birefringent film. In the case where the antireflection film is a multilayer thin film including a high refractive film and a low refractive film, the protective film formed on the birefringent film functions as a high refractive film or a low refractive film which is a part of the antireflection film.

For example, in the formation of SiO₂(refractive index 1.5) as a protective film, in an antireflection film including a high refractive film and a low refractive film, the protective film functions as a low refractive film. In this case, in step S4, the material is formed of SiO₂Forming SiO with refractive index ratio on the low refractive film composed of the protective film₂High TiO content₂(refractive index 2.4) and the like.

Thus, a birefringent film having a columnar portion and a gap portion stacked in a columnar shape by oblique deposition is formed, and after annealing treatment is performed on the birefringent layer at a temperature of 100 ℃ to 300 ℃, a protective film formed by forming an inorganic compound at a high density is formed on the birefringent layer, whereby the amount of birefringence can be increased, and a wavelength plate exhibiting excellent stability with high moisture resistance can be obtained as compared with the conventional wavelength plate.

The wavelength plate of the present embodiment thus manufactured can be used for optical devices such as liquid crystal projectors, and can cope with high optical density, so that the optical unit portion can be downsized.

The present embodiment has been described above, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention.

Examples

< 4. example >

Next, specific examples of the present invention will be explained. The scope of the present invention is not limited to the following examples.

< example 1 >

Ta is deposited on a glass substrate with a deposition source at 70 DEG with respect to the normal direction of the glass substrate surface₂O₅The columnar portion is formed as a dielectric material. Next, annealing treatment was performed at a temperature of 200 ℃ to evaporate water adsorbed between the columnar portions (gap portions). SiO is formed on a birefringent film including a columnar portion and a gap portion formed on a glass substrate by a CVD method₂As the protective film, a sample of the wavelength plate of example 1 was produced.

In order to examine the safety of the sample of the produced wavelength plate, the sample was held for 100 hours (h) in an environment having a temperature of 60 ℃ and a humidity of 90% as a moisture resistance load test. Fig. 10 shows the transmittance immediately after completion of the sample (curve (a)) and the transmittance after retention for 100 hours in the moisture resistance load test (curve (B)) for the sample of the wavelength plate of example 1. As shown in fig. 10, in the sample of the wavelength plate of example 1, no difference in transmittance was generated between immediately after completion of the sample and after the moisture resistance load test.

FIG. 11 is a graph showing the transmittance at a wavelength of 550nm of a sample of the wavelength plate of example 1 and a sample of the wavelength plate produced in the same manner as in example 1 except that the annealing temperature was changed to 25 ℃, 100 ℃, 300 ℃ and 400 ℃. In general, the transmittance of the wavelength plate is required to be 90% or more in view of the characteristics of the wavelength plate, but as shown in fig. 11, the highest transmittance (92% or more) can be achieved in the samples of the wavelength plate of example 1.

In example 1, after annealing treatment was performed at a temperature of 200 ℃, SiO was formed at high density by CVD₂The obtained protective film with low moisture permeability can be used to manufacture wavelength plate with high moisture resistance, and has good durability and stability.

< comparative example 1 >

SiO is formed by resistance heating deposition method except for the birefringent layer including the columnar portion and the gap portion formed on the glass substrate₂A sample of a wavelength plate was produced in the same manner as in example 1 except for using the protective film. Specifically, SiO is supplied to the heat generating resistor₂Heating and evaporating it to form evaporated SiO₂The particles were attached to the surface of the birefringent layer on the substrate to form a protective film, and a sample of the wavelength plate of comparative example 1 was prepared.

A moisture resistance load test (holding for 100 hours (h) in an environment of 60 ℃ C. and 90% humidity) was carried out in the same manner as in example 1 using the sample of the wavelength plate of comparative example 1. Fig. 12 shows the transmittance immediately after completion of the sample of the wavelength plate of comparative example 1 (curve (a)) and the transmittance after 100 hours of retention in the moisture resistance load test (curve (B)). As shown in FIG. 12, in the sample of the wavelength plate of comparative example 1, the transmittance after the moisture resistance load test is reduced in the region of a wavelength of about 400nm to 850nm as compared with the transmittance immediately after the completion of the sample.

In comparative example 1, since the protective film was formed by the resistance heating deposition method, it was not possible to form SiO with high density₂The protective film cannot be made to have low moisture permeability. Therefore, the manufactured wavelength plate has low moisture resistance, durability and stabilityThe performance is poor.

< comparative example 2 >

A sample of a wavelength plate was produced in the same manner as in example 1, except that no protective film was formed on the birefringent film including the columnar portions and the gap portions formed on the glass substrate.

A moisture resistance load test (keeping at 60 ℃ C. and 90% humidity for 100 hours (h)) was carried out in the same manner as in example 1. Fig. 13 shows the transmittance immediately after completion of the sample of the wavelength plate of comparative example 2 (curve (a)) and the transmittance after 100 hours of retention in the moisture resistance load test (curve (B)). As shown in fig. 13, in the sample of the wavelength plate of comparative example 2, in most of the region having a wavelength of about 350nm to 850nm, the transmittance after the moisture resistance load test was reduced as compared with the transmittance immediately after the completion of the sample. In addition, in the sample of the wavelength plate of comparative example 2, cracks were generated in the fine particles in the columnar portion.

In comparative example 2, since no protective film was formed, the produced wavelength plate was low in moisture resistance and poor in durability and stability.

< application example 1 >

A wavelength plate having a fine pattern formed thereon was fabricated on a glass substrate provided with one-dimensional squares having a pitch of 150nm and a depth of 50 nm. Then, the effect of the fine pattern was evaluated. The deposition angle in the direction perpendicular to the line of the one-dimensional square and in the normal direction to the glass substrate surface was 70 degrees, and Ta was deposited obliquely₂O₅As a dielectric material, 1-layer birefringent film was formed. The thickness of the birefringent film was 1.2. mu.m. In addition, similarly to this, a flat substrate on which no fine pattern is formed is used, and a birefringent film is formed on the flat substrate.

Fig. 14 is a graph showing a comparison of birefringence amounts of a wavelength plate using a one-dimensional checkered substrate and a wavelength plate using a flat substrate. FIG. 15 is an SEM (Scanning Electron Microscope) image of a cross section of a wavelength plate using a one-dimensional square substrate.

The wavelength plate using the one-dimensional checkered substrate has a birefringence 2.8 times as large as that of the conventional inclined deposition using a flat substrate. This is considered to be because the film is formed on the one-dimensional square substrate, and thus the interval occurs between squares, increasing the effect of structural birefringence.

According to the wavelength plate using the one-dimensional checkered substrate, the film can be made thinner than the conventional one in order to obtain desired phase characteristics. Further, the reduction in film thickness has many advantages such as the speeding up and the effectiveness of the production process and the reduction in material cost for film formation.

Description of the symbols

1 wavelength plate, 11 substrates, 12 columnar parts, 13 gap parts, 14 birefringent layers, 15 protective films.

Claims (7)

1. A method for manufacturing a wavelength plate, comprising:

a birefringent layer forming step of depositing a dielectric material on a substrate in a tilted manner to form a birefringent layer having columnar portions in which microparticles of the dielectric material are stacked in columnar form and gap portions provided between the columnar portions;

an annealing step of annealing the birefringent layer at a temperature of 100 ℃ to 300 ℃; and

and a protective film forming step of forming a protective film by forming an inorganic compound at a high density on the annealed birefringent layer.

2. The method of manufacturing a wavelength plate according to claim 1,

in the protective film forming step, the protective film is formed on the birefringent layer by any one of a chemical deposition method, a plasma assist method, and a sputtering method.

3. A method of manufacturing a wavelength plate according to claim 1 or claim 2,

further comprising a high refractive index film forming step of forming a high refractive index film having a refractive index higher than that of the protective film on the protective film,

forming an antireflection film including the protective film and the high refractive film.

4. The method of manufacturing a wavelength plate according to any one of claims 1 to 3,

the inorganic compound is SiO₂。

5. The method of manufacturing a wavelength plate according to any one of claims 1 to 4,

the dielectric material is Ta₂O₅。

6. The method of manufacturing a wavelength plate according to any one of claims 1 to 5,

the substrate is formed with periodic concave and convex portions at a wavelength of light or less, and the dielectric material is obliquely deposited on the convex portions in the birefringent layer forming step.

7. The method of manufacturing a wavelength plate according to any one of claims 1 to 6,

in the birefringent layer forming step, at least 2 or more birefringent layers are stacked, the stacking direction of which is sequentially reversed by 180 °.