A light source module includes at least one light-emitting element, a first optical layer, a penetrating light selection layer, a second optical layer, a light splitting layer, and a wavelength conversion layer. The light-emitting element is configured to provide a beam with a wavelength falling within a first wavelength band. An exit angle at which the beam exits the first optical layer is greater than an incident angle at which the beam is incident to the first optical layer. The penetrating light selection layer may allow light with a wavelength falls within a second wavelength band to pass through and has corresponding transmittance for light with a wavelength falling within the first wavelength band and is incident at different incident angles. An exit angle at which the beam exits the second optical layer is less than an incident angle at which the beam is incident to the second optical layer.

Provided is compatibility between adhesion to a substrate (lower layer) and durability improvement. An optical element includes a phosphor layer facing a lower layer, and a bonding layer keeping the phosphor layer in intimate contact with the lower layer. The phosphor layer includes an inorganic binder, and phosphor particle dispersed with the inorganic binder. The bonding layer includes an organic binder. The phosphor layer has a first surface facing the lower layer, a second surface opposite to the first surface, and a side surface connecting the first and second surfaces together. The bonding layer connects together the second surface, the side surface, and a surface of the lower layer to keep the phosphor layer in intimate contact with the lower layer.

A fluorescent module includes a fluorescent member including a phosphor-containing layer, and a light reflecting layer disposed on the phosphor-containing layer. The phosphor-containing layer contains a YAG phosphor and a Ga-YAG phosphor within the same layer, the Ga-YAG phosphor being a phosphor in which a portion of the aluminum constituting the YAG phosphor is substituted with gallium. A volumetric ratio of the Ga-YAG phosphor to the entirety of the YAG phosphor and the Ga-YAG phosphor is in a range of 19.0% to 80%.

A wavelength conversion member includes a ceramic fluorescent body for converting a wavelength of incident light, a heat radiation member for radiating heat of the ceramic fluorescent body to an outside atmosphere, and a solder layer for joining together the ceramic fluorescent body and the heat radiation member. The solder layer includes a joining portion disposed between the ceramic fluorescent body and the heat radiation member and a protruding portion protruding outward from an outer circumferential portion of the ceramic fluorescent body. The protruding portion is spaced apart from a side surface formed on the outer circumferential portion of the ceramic fluorescent body. In the solder layer, the maximum value of thickness of the protruding portion is greater than the average value of thickness of the joining portion.

A wavelength conversion member includes a ceramic fluorescent body for converting a wavelength of incident light, a heat radiation member for radiating heat of the ceramic fluorescent body to an outside atmosphere, and a solder layer for joining together the ceramic fluorescent body and the heat radiation member. The solder layer includes a joining portion disposed between the ceramic fluorescent body and the heat radiation member and a protruding portion protruding outward from an outer circumferential portion of the ceramic fluorescent body. The protruding portion is spaced apart from a side surface formed on the outer circumferential portion of the ceramic fluorescent body. In the solder layer, the maximum value of thickness of the protruding portion is greater than the average value of thickness of the joining portion.

Provided is a polymerizable composition including a quantum dot, a polyfunctional thiol, a first (meth)acrylate, and a second (meth)acrylate, in which the first (meth)acrylate is a polyfunctional (meth)acrylate, the second (meth)acrylate is a mono- or higher functional (meth)acrylate having a functional group selected from the group consisting of a carboxy group, a hydroxy group, a phosphate group, and an amino group, and a molecular weight of the second (meth)acrylate is equal to or less than a molecular weight of the polyfunctional thiol.

Provided is a method including: preparing a substrate having a first surface; preparing a wavelength conversion layer that converts a light of a first wavelength band into a light of a second wavelength band different from the light of the first wavelength band; preparing a bonding material including a metal fine particle and a surface stabilizer formed at a surface of the metal fine particle and decomposed by oxygen; forming a protective film protecting the first surface while the protective film generates a gas containing hydrogen; releasing, from one of the protective film and the substrate, the gas occluded by the one of the protective film and the substrate in the forming of the protective film; and bonding the substrate and the wavelength conversion layer via the bonding material by metal sintering.

Provided is a method including: preparing a substrate having a first surface; preparing a wavelength conversion layer that converts a light of a first wavelength band into a light of a second wavelength band different from the light of the first wavelength band; preparing a bonding material including a metal fine particle and a surface stabilizer formed at a surface of the metal fine particle and decomposed by oxygen; forming a protective film protecting the first surface while the protective film generates a gas containing hydrogen; releasing, from one of the protective film and the substrate, the gas occluded by the one of the protective film and the substrate in the forming of the protective film; and bonding the substrate and the wavelength conversion layer via the bonding material by metal sintering.

A lighting device is provided that includes light emitting unit that emits primary light and a light conversion element that is illuminated with the primary light and emits secondary light of another wavelength. The light conversion element has a front side defining a primary light receiving surface that received the primary light and a secondary light emitting surface that emits the secondary light. The light conversion element has a variable thickness at the primary light receiving surface and/or in the secondary light emitting surface.

A lighting device is provided that includes light emitting unit that emits primary light and a light conversion element that is illuminated with the primary light and emits secondary light of another wavelength. The light conversion element has a front side defining a primary light receiving surface that received the primary light and a secondary light emitting surface that emits the secondary light. The light conversion element has a variable thickness at the primary light receiving surface and/or in the secondary light emitting surface.